# GCN_circulars

GRB_name: GRB210503A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29927
SUBJECT: GRB 210503A: Fermi GBM Final Real-time Localization
DATE:    21/05/03 19:44:33 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 19:34:09 UT on 3 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210503A (trigger 641763254.461374 / 210503815).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 328.9, Dec = 66.0 (J2000 degrees, equivalent to J2000 21h 55m, 66d 00'), with a statistical uncertainty of 5.1 degrees.

The angle from the Fermi LAT boresight is 32.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210503815/quicklook/glg_skymap_all_bn210503815.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210503815/quicklook/glg_healpix_all_bn210503815.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210503815/quicklook/glg_lc_medres34_bn210503815.gif


GRB_name: GRB210503A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29928
SUBJECT: Fermi GRB 210503A: Global MASTER-Net observations report 
DATE:    21/05/03 20:30:21 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210503A ( Fermi GBM team, GCN 29927) errorbox  553 sec after notice time and 580 sec after trigger time at 2021-05-03 19:43:49 UT, with upper limit up to  18.6 mag. The observations began at zenith distance = 65 deg. The sun  altitude  is -28.1 deg. 

The galactic latitude b =  9 deg., longitude l = 107 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1606239

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     640 | 2021-05-03 19:43:49 |   MASTER-Kislovodsk | (22h 04m 41.61s , +65d 36m 00.0s) |   C |   120 | 17.8 |        
     795 | 2021-05-03 19:43:49 |   MASTER-Kislovodsk | (22h 04m 41.62s , +65d 36m 00.1s) |   C |   430 | 18.2 |  Coadd 
     641 | 2021-05-03 19:43:50 |   MASTER-Kislovodsk | (21h 55m 16.11s , +66d 01m 20.5s) |   C |   120 | 17.4 |        
     796 | 2021-05-03 19:43:50 |   MASTER-Kislovodsk | (21h 55m 16.11s , +66d 01m 20.6s) |   C |   430 | 17.9 |  Coadd 
     791 | 2021-05-03 19:46:10 |   MASTER-Kislovodsk | (21h 55m 13.86s , +66d 02m 59.4s) |   C |   140 | 17.4 |        
     791 | 2021-05-03 19:46:10 |   MASTER-Kislovodsk | (22h 04m 39.81s , +65d 37m 37.1s) |   C |   140 | 17.6 |        
     966 | 2021-05-03 19:48:50 |   MASTER-Kislovodsk | (21h 55m 14.30s , +66d 01m 26.2s) |   C |   170 | 17.5 |        
     966 | 2021-05-03 19:48:50 |   MASTER-Kislovodsk | (22h 04m 39.77s , +65d 36m 02.5s) |   C |   170 | 17.6 |        
    1161 | 2021-05-03 19:52:00 |   MASTER-Kislovodsk | (21h 55m 17.75s , +66d 02m 50.4s) |   C |   180 | 16.9 |        
    1162 | 2021-05-03 19:52:00 |   MASTER-Kislovodsk | (22h 04m 43.87s , +65d 37m 25.6s) |   C |   180 | 17.0 |        
    2005 | 2021-05-03 20:07:04 |   MASTER-Kislovodsk | (21h 37m 10.39s , +66d 01m 47.0s) |   C |    60 | 17.8 |        
    2005 | 2021-05-03 20:07:04 |   MASTER-Kislovodsk | (21h 47m 15.11s , +65d 35m 53.1s) |   C |    60 | 18.1 |        
    2085 | 2021-05-03 20:08:24 |   MASTER-Kislovodsk | (22h 02m 55.09s , +68d 00m 35.5s) |   C |    60 | 17.3 |        
    2085 | 2021-05-03 20:08:24 |   MASTER-Kislovodsk | (22h 13m 49.89s , +67d 34m 30.0s) |   C |    60 | 17.6 |        
    2165 | 2021-05-03 20:09:44 |   MASTER-Kislovodsk | (21h 52m 55.00s , +64d 01m 52.3s) |   C |    60 | 17.6 |        
    2165 | 2021-05-03 20:09:44 |   MASTER-Kislovodsk | (22h 02m 14.69s , +63d 36m 02.4s) |   C |    60 | 17.9 |        
    2245 | 2021-05-03 20:11:04 |   MASTER-Kislovodsk | (22h 16m 27.15s , +66d 00m 24.9s) |   C |    60 | 17.5 |        
    2245 | 2021-05-03 20:11:04 |   MASTER-Kislovodsk | (22h 26m 29.07s , +65d 34m 25.8s) |   C |    60 | 17.7 |        
    2326 | 2021-05-03 20:12:25 |   MASTER-Kislovodsk | (21h 20m 16.68s , +68d 00m 22.7s) |   C |    60 | 17.7 |        
    2326 | 2021-05-03 20:12:25 |   MASTER-Kislovodsk | (21h 31m 11.18s , +67d 34m 26.7s) |   C |    60 | 18.2 |        
    2406 | 2021-05-03 20:13:45 |   MASTER-Kislovodsk | (21h 48m 48.66s , +70d 00m 16.6s) |   C |    60 | 17.9 |        
    2406 | 2021-05-03 20:13:45 |   MASTER-Kislovodsk | (22h 00m 44.35s , +69d 34m 04.3s) |   C |    60 | 18.4 |        
    2686 | 2021-05-03 20:18:25 |   MASTER-Kislovodsk | (22h 38m 42.00s , +63d 34m 18.9s) |   C |    60 | 18.0 |        
    2686 | 2021-05-03 20:18:25 |   MASTER-Kislovodsk | (22h 29m 29.94s , +63d 59m 46.5s) |   C |    60 | 17.6 |        
    2767 | 2021-05-03 20:19:46 |   MASTER-Kislovodsk | (22h 08m 18.67s , +62d 01m 27.6s) |   C |    60 | 17.7 |        
    2767 | 2021-05-03 20:19:46 |   MASTER-Kislovodsk | (22h 16m 54.68s , +61d 36m 05.7s) |   C |    60 | 18.2 |        
    2847 | 2021-05-03 20:21:06 |   MASTER-Kislovodsk | (21h 16m 33.92s , +64d 01m 43.6s) |   C |    60 | 18.1 |        
    2847 | 2021-05-03 20:21:06 |   MASTER-Kislovodsk | (21h 25m 48.93s , +63d 36m 22.4s) |   C |    60 | 18.6 |        
    2927 | 2021-05-03 20:22:26 |   MASTER-Kislovodsk | (21h 47m 08.96s , +65d 36m 48.0s) |   C |    60 | 18.5 |        
    2927 | 2021-05-03 20:22:26 |   MASTER-Kislovodsk | (21h 37m 11.26s , +66d 02m 19.3s) |   C |    60 | 18.0 |        
    3007 | 2021-05-03 20:23:46 |   MASTER-Kislovodsk | (22h 03m 09.27s , +68d 00m 46.9s) |   C |    60 | 17.7 |        
    3007 | 2021-05-03 20:23:46 |   MASTER-Kislovodsk | (22h 13m 56.78s , +67d 35m 04.6s) |   C |    60 | 18.2 |        
    3087 | 2021-05-03 20:25:06 |   MASTER-Kislovodsk | (21h 53m 02.84s , +64d 00m 05.4s) |   C |    60 | 17.9 |        
    3087 | 2021-05-03 20:25:06 |   MASTER-Kislovodsk | (22h 02m 15.96s , +63d 34m 40.4s) |   C |    60 | 18.3 |        
    3167 | 2021-05-03 20:26:26 |   MASTER-Kislovodsk | (22h 26m 30.72s , +65d 34m 32.3s) |   C |    60 | 18.2 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210504A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29929
SUBJECT: GRB 210504A: Swift detection of a burst
DATE:    21/05/04 14:39:18 GMT
FROM:    Phil Evans at U of Leicester  <pae9@star.le.ac.uk>

A. P. Beardmore (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

Swift Burst Alert Telescope (BAT) triggered and located GRB 210504A
(trigger=1046782), with the trigger time most likely between 13:40
and 13:58 UT. No BAT information is available at this moment. 

XRT began observing the field of the new trigger at 13:58:28 UT. 
In a promptly-downlinked image we find an X-ray source at
RA,Dec = 222.3933, -30.5322 which is equivalent to 

RA (J2000)  = 14:49:34.4
Dec (J2000) = -30:31:56

with an estimated uncertainty of about 10". 

We currently have very limited data products and are awaiting the 
full data after a ground station pass to further characterise
this object. 

UVOT took a finding chart exposure of â€‹150 seconds with the â€‹white filter. 
No credible afterglow candidate has been found in the initial data products. 
The 2.7'x2.7' sub-image covers none of the XRT error circle. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. 
No correction has been made for extinction in the Milky Way. 

Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210504A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29930
SUBJECT: GRB 210504A: update on the BAT trigger time and burst duration
DATE:    21/05/04 17:11:37 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC), A. P. Beardmore (U Leicester),
and K. L. Page (U Leicester) report on behalf of the Neil Gehrels
Swift Observatory Team:

We received further data from recent telemetry downlink.
The trigger time for GRB 210504A (Swift trigger #1046782;
Beardmore et al., GCN Circ. 29929) is
2021-05-04T13:54:53 UTC.

Based on currently available data from T-60 to T+63 sec,
the burst duration is longer than 50 seconds.


GRB_name: GRB210504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29932
SUBJECT: GRB 210504A: BOOTES-4/MET optical upper limit
DATE:    21/05/04 20:17:35 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210504A by Swift (Beardmore et al. GCNC 29929), we triggered the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) in order to follow up this burst, starting on May 4, 16:05 UT (~2.2 hr after the BAT trigger, according to Lien et al. GCNC 29930). No optical source is detected within the XRT error box (Beardmore et al. GCNC 29929) down to 19.1 mag in the co-added image (630 s in total, clear filter). This non-detection is consistent with the UVOT (Beardmore et al. GCNC 29929) and MASTER (Lipunov et al. GCNC 29931) limits.

We thank the staff at Lijiang observatory for their excellent support.


GRB_name: GRB210504A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29933
SUBJECT: GRB 210504A: Swift/UVOT Detection
DATE:    21/05/04 20:42:29 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210504A 218 s after the BAT trigger 
(Beardmore et al., GCN Circ. 29929). A fading source is detected in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  14:49:34.03 = 222.39179 (deg.)
     Dec (J2000) = -30:32:02.2  = -30.53395 (deg.)
with an estimated uncertainty of 0.6 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 
2011, AIP Conf. Proc. 1358, 373) for the early exposures are:

Filter T_start(s) T_stop(s)     Exp(s)    Mag +/-
white     218      368           147      19.75 0.19
white    1168     1877            97      20.08 0.31
v         374      739            58     >18.26
b         473      837            58     >19.29
b        1144     1852            97      19.17 0.25
u         448      812            58     >18.89
uvw1      424      788            58     >18.49
uvm2      399      418            20     >17.24
uvw2      523     1040            59     >18.60


GRB_name: GRB210504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29934
SUBJECT: GRB 210504A: AST3-3 YaoAn Optical Upper Limit
DATE:    21/05/04 22:44:24 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS  <trsun@pmo.ac.cn>

Tianrui Sun(Purple Mountain Observatory), Lei Hu, Maokai Hu, Xuefeng Wu, Lei Liu, Kelai Meng, Xiaoyan Li(Nanjing Institute of Astronomical Observation Technology), Zhengyang Li, Xiangyan Yuan, Lifan Wang(TAMU), Xiaofeng Wang (Tsinghua University), report on behalf the AST3 Team:


Following the detection of GRB 210504A by Swift (Beardmore et al. GCNC 29929), we use Antarctic Survey Telescope 3-3 at YaoAn Astronomy Observation (China, Yunnan) for follow-up. Our observation started on 2021-05-04T16:02:29.850 (about 2 hours after the trigger of BAT, according to Lien et al. GCNC 29930). No optical source was detected within the XRT error box down to 21.0 +/- 0.6 mag in the coadded image (total 2100s, g-band). Our non-detection result is consistent with the UVOT (Beardmore et al. GCNC 29929), MASTER (Lipunov et al. GCNC 29931), and the BOOTES-4/ MET (Hu et al. GCNC 29932) limits.


GRB_name: GRB210503A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29935
SUBJECT: Fermi GRB 210503A: DDOTI Upper Limits on the Afterglow
DATE:    21/05/04 22:48:23 GMT
FROM:    Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada  <mpereyra@astro.unam.mx>

Margarita Pereyra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM),
Eleonora Troja (GSFC/UMD),  Simone Dichiara (GSFC/UMD), Rosa L. Becerra
(UNAM), William H. Lee (UNAM), OcÃ©lotl LÃ³pez,  Diego Gonzalez (UNAM),
Alexander Kutyrev (GSFC/UMD), and Srihari Ravi (ASU), report:

We observed the field of the likely long Fermi GRB 210503A (trigger
641763254, GCN #29927, Fermi GBM Team) with the DDOTI/OAN wide-field imager
at the Observatorio AstronÃ³mico Nacional on Sierra San Pedro MÃ¡rtir (
http://ddoti.astroscu.unam.mx) on 2021-05-04 from 07:02 to 11:38 UTC (11.5
to   16 hours after the event).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position 328.93d
+66.03d (J2000). This region contains 6 instrumental fields or about 400
square degrees. We obtained 1560 seconds of exposure per instrumental field
in the w filter. We obtained AB photometry by calibration against the APASS
catalog.

We detect no likely candidate for the afterglow to our 10-sigma upper
limits of

w = 19.32 to 19.93 (interquartile range).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.

--


GRB_name: GRB210504A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29936
SUBJECT: GRB 210504A: MITSuME Akeno optical upper limits
DATE:    21/05/04 23:35:54 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, Y. Imai,
S. Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210504A (Beardmore et al. GCN Circular #29929, Lien
 et al. GCN Circular #29930) with the optical three color (g', Rc, and
Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno
Observatory, Yamanashi, Japan. The observation with a series of 60 sec
exposures started at 2021-05-04 14:55:16 UT (1.0 hour after the BAT
trigger, Lien et al. GCN Circular #29930). We stacked the images with
good conditions. We did not detect any uncatalogued sources within the
XRT error circle (Beardmore et al. GCN Circular #29929) in all three
bands. We obtained the 5-sigma limits of the stacked images as
follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
1.1 2021-05-04 15:01 300 gâ€™>15.9, Rc>16.2, Ic>15.9
2.8 2021-05-04 16:42 2580 gâ€™>18.3, Rc>18.7, Ic>18.3
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time

We used the PS1 catalog for flux calibration. The magnitudes are
expressed in the AB system. The images were processed in real-time
through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ,
Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29937
SUBJECT: GRB 210504A: NOT optical afterglow detection
DATE:    21/05/05 00:15:45 GMT
FROM:    Daniel Perley at Liverpool JMU  <d.a.perley@ljmu.ac.uk>

K. E. Heintz (Univ. of Iceland and DAWN/NBI), D. A. Perley (LJMU), D. B. 
Malesani (DTU Space), and A. A. Djupvik (NOT) report on behalf of a 
larger collaboration:

We observed the location of the optical and X-ray afterglow of GRB 
210504A (Beardmore et al., GCN 29929; Breeveld & Beardmore, GCN 29933) 
using the Nordic Optical Telescope (NOT) equipped with the ALFOSC
camera.  We obtained 3x300 s frames in the Sloan r-band filter, followed 
by 5x200s frames in the z-band filter.  Observations were carried out on 
2021-05-04 UT between 23:10 and 23:35 (9.3 hours after the BAT trigger 
time given by Lien et al. (GCN 29930).

The optical afterglow is detected in the combined images.  We report a 
refined position (J2000) of:

RA:   14:49:34.04
Dec: -30:32:02.6

No source is visible at this location in Pan-STARRS reference imaging.

The r-band magnitude of the afterglow at the time of the observation is 
measured to be 20.95 +/- 0.05.









DisclaimerNone


GRB_name: GRB210504A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29939
SUBJECT: GRB 210504A: Swift-BAT refined analysis
DATE:    21/05/05 02:27:49 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J. R. Cummings (CPI),
H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210504A (trigger #1046782)
(Beardmore et al., GCN Circ. 29929).  The BAT ground-calculated position is
RA, Dec = 222.379, -30.557 deg which is
   RA(J2000)  =  14h 49m 31.0s
   Dec(J2000) = -30d 33' 23.5"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.

The mask-weighted light curve shows several overlapping pulses
that start at ~T-30 s and end at ~T+150 s. There might be additional
burst emission before the GRB came into the BAT FOV at ~T-43 s.
T90 (15-350 keV) is 135.06 +- 9.57 sec (estimated error including
systematics).

The time-averaged spectrum from T-27.55 to T+134.76 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.64 +- 0.13.  The fluence in the 15-150 keV band is
2.7 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+87.68 sec in the 15-150 keV band is 0.9 +- 0.2 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1046782/BA/


GRB_name: GRB210504A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29942
SUBJECT: GRB 210504A: Swift-XRT refined Analysis
DATE:    21/05/05 04:52:24 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU), J.P. Osborne
(U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), T.
Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and A.P. Beardmore report
on behalf of the Swift-XRT team:

We have analysed 6.7 ks of XRT data for GRB 210504A (Beardmore et al.
GCN Circ. 29929), from 218 s to 24.9 ks after the  BAT trigger. The
data comprise 146 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 2804 s of PC mode data and 3 UVOT
images, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
222.39118, -30.53345 which is equivalent to:

RA (J2000): 14h 49m 33.88s
Dec(J2000): -30d 32' 00.4"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

The late-time light curve (from T0+11.6 ks) can be modelled with a
power-law decay with a decay index of alpha=1.9 (+/-0.8).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.00 (+0.13, -0.11). The
best-fitting absorption column is  1.50 (+0.41, -0.20) x 10^21 cm^-2,
consistent with the Galactic value of 1.3 x 10^21 cm^-2 (Willingale et
al. 2013). The PC mode spectrum has a photon index of 2.11 (+0.25,
-0.16) and a best-fitting absorption column of 1.35 (+0.75, -0.06) x
10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 3.1 x 10^-11 (4.2 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.35 (+0.75, -0.06) x 10^21 cm^-2
Galactic foreground: 1.3 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.11 (+0.25, -0.16)

If the light curve continues to decay with a power-law decay index of
1.9, the count rate at T+24 hours will be 1.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.3 x
10^-14 (4.4 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01046782.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210424B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29943
SUBJECT: GRB 210424B: AstroSat CZTI detection
DATE:    21/05/05 04:55:36 GMT
FROM:    Varun Bhalerao at Indian Inst of Tech  <varunb@iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta (IITB), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al, 2020, arxiv:2011.07067) showed a strong detection of a short GRB 210424B, which was also detected by IPN (GCN #29909) and Konus-Wind (GCN #29911).

The source was clearly detected in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-24 08:01:55.150 UT. The measured peak count rate associated with the burst is 2260 (+322, -98) cts/s above the background using 0.1s bins in the combined data of four quadrants, with a total of 1380 (+96, -118) cts. The local mean background count rate was 530 (+9, -11) cts/s. Using cumulative rates, we measure a T90 of 1.24 (+0.13, -0.40)s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2021-04-24 08:01:54.535 UT. The measured peak count rate is 1244 (+89, -98) cts/s above the background in the combined Veto data of four quadrants, with a total of 1822 (+351, -377) cts. The local mean background count rate was 1895 (+5, -6) cts/s. We measure a T90 of 7 (+4, -5) s from the cumulative Veto light curve, though this is most likely an overestimate due to the intrinsic 1s binning of veto data.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.


GRB_name: GRB210504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29944
SUBJECT: GRB 210504A: VLT X-shooter redshift
DATE:    21/05/05 07:36:20 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. Xu (NAOC), P. Schady (Univ. Bath), K. E. Heintz (Univ. Iceland and 
DAWN/NBI), D. B. Malesani (DTU Space), B. Sbarufatti (PSU), G. Pugliese 
(API, Univ. Amsterdam), D. A. Perley (LJMU), V. D'Elia (ASI/SSDC, 
INAF/OAR), D. A. Kann (HETH/IAA-CSIC), and J. P. U. Fynbo (DAWN/NBI/DTU) 
report on behalf of the Stargate consortium:

We observed the optical afterglow (Breeveld & Beardmore, GCN 29933; 
Heintz et al., GCN 29937) of GRB 210504A (Beardmore et al., GCN 29929; 
Lien et al., GCN 29330) using the ESO VLT UT3 (Melipal) equipped with 
the X-shooter spectrograph. Our spectra cover the wavelength range 
3000-21000 AA, and consist of 4 exposures of 1200 s each (8 x 600 s in 
the NIR). The observation mid-time was 2021 May 05.06 UT (11.6 hr after 
the GRB).

In a 60 s image taken with the acquisition camera on May 05.02 UT, we 
detect the optical afterglow, for which we measure an AB magnitude r' = 
21.11 +- 0.04 mag (calibrated against nearby stars from the Pan-STARRS 
catalog).

We clearly detect continuum over the wavelength range of the entire 
spectrum. A trough is visible around 3740 AA, which we identify as due 
to H I. From the detection of several absorption features, which we 
interpret as due to Si II, C II, C IV, Fe II, Al II, Mg II, among 
others, as well as the Lyman forest, we infer a redshift z = 2.077.

We acknowledge excellent support from the observing staff at Paranal, in 
particular Steffen Mieske, Ditte Slumstrup and Diego Parraguez.


GRB_name: GRB210504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29946
SUBJECT: GRB 210504A: Lowell Discovery Telescope optical observations
DATE:    21/05/05 14:36:48 GMT
FROM:    Brendan O'Connor at UMD  <oconnorb@umd.edu>

B. O'Connor (UMD, GWU), S.Dichiara (UMD, NASA-GSFC), E. Troja
(UMD, NASA-GSFC), P. Gatkine (Caltech), J.M. Durbak (UMD), S.B. Cenko
(NASA-GSFC), A. Kutyrev (UMD, NASA-GSFC), S. Veilleux (UMD) report:

We observed the field of the GRB 210504A (Beardmore et al., GCN 29929;
Lien et al., GCN 29930) using the Large Monolithic Imager (LMI) on the
4.3m Lowell Discovery Telescope (LDT) at Happy Jack, AZ. Observations
started on May 5, 2021 at 06:32:14 UT (about 16.6 hours after the Swift
trigger) using the SDSS g, r, i, and z filters. Observations were taken at
an
airmass of 2.5 and seeing of about 1.5".

We detect the optical counterpart identified by the Swift/UVOT
(Breeveld et al., GCN 29933), the NOT (Heintz et al., GCN 29937),
and VLT (Xu et al., GCN 29944). The afterglow has magnitude r ~ 21.66
+/- 0.04 AB mag and i ~ 21.43 +/- 0.03 AB mag.

Magnitudes are calibrated against the PanSTARRS catalog and are not
corrected for Galactic extinction.

We thank the staff of the Lowell Discovery Telescope for assistance
with these observations.


GRB_name: GRB210506A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29947
SUBJECT: GRB 210506A: Swift/BAT-GUANO detection and possible arcminute localization of a short hard burst
DATE:    21/05/06 06:54:35 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), Jamie A. Kennea
(PSU) report:

Swift/BAT did not trigger on GRB 210506A (T0: 2021-05-06 00:39:48.54
UTC, INTEGRAL/SPI-ACS trigger 9191).

The INTEGRAL/SPI-ACS notice, distributed in near real-time triggered
the Swift Mission Operations Center operated Gamma-ray Urgent Archiver
for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 90 seconds of BAT event-mode data from
[-45,+45] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is strongly detected in BAT with a duration of ~0.2 seconds.

The position of the burst was found with the typical BAT imaging
procedure with an SNR of 6.8.
We note that this position would imply an extremely hard spectrum for
this burst, beyond what is typically expected. This could imply that
the position is incorrect, or that this is a truly exceptional event.
We encourage other GRB instruments to provide spectral measurements
that can help clarify the situation.

The BAT position is
RA, Dec = 132.853, 4.582 deg which is
   RA(J2000)  = 08h 51m 24.72s
   Dec(J2000) =  04d 34â€™ 55.2â€
with an estimated uncertainty of 4 arcmin.

XRT and UVOT follow-up has been requested. Results of follow-up
observations will be reported in future circulars.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/


GRB_name: GRB210506A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29949
SUBJECT: GRB 210506A: Swift ToO observations
DATE:    21/05/06 09:58:18 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 210506A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021430

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210506A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29955
SUBJECT: GRB 210506A: TNG NIR upper limits
DATE:    21/05/07 00:15:10 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo (INAF-OAB), V. D'Elia (ASI-SSDC), D. Malesani (DTU Space), E. Palazzi, A. Rossi (INAF-OAS), 
G. Andreuzzi, D. Carosati (INAF-TNG) on behalf of the CIBO collaboration report:

We observed the field of the short GRB 210506A (Tohuvavohu & DeLaunay, GCN Circ. 29947) with the Italian 3.6m TNG 
telescope equipped with NICS in imaging mode. A series of images were obtained with the J filter on 2021-05-06 from 
21:15:04 UT to 21:55:59 UT (i.e. at a mid time of about 20.9 hours after the burst). 

Our observations (with a field of view of 4.2' x 4.2') were centered at the position of the XRT source #3 
(see: https://www.swift.ac.uk/ToO_GRBs/00021430/ and Evans, GCN Circ. 29949). 

No obvious source is found within the position of source XRT #3 down to a 3-sigma limiting magnitude of J > 20.6 
(Vega, calibrated against the 2MASS catalogue). 
Unfortunately an image artefact, possibly due to bad sky subtraction, prevented us to visually investigate a portion 
(~ 5%) of the XRT error circle for source #3. 


GRB_name: GRB210506A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29956
SUBJECT: GRB 210506A: Nanshan/NEXT optical upper limit
DATE:    21/05/07 03:12:02 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), X. Liu, D. Xu (NAOC), X. Gao 
(Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 210506A (Tohuvavohu, DeLaunay & Kennea, GCN 
29947) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, 
China. We obtained 9x300 s frames in the Sloan r-band, starting at 
15:17:27 UT on 2021-05-06, i.e., 14.63 hr after the BAT trigger.

No credible optical source is detected in our stacked image at the 
position of the XRT source #3 that lies in the BAT error circle (ref. 
https://www.swift.ac.uk/ToO_GRBs/00021430/ and Evans, GCN 29949), down 
to a limiting magnitude of r~21.7, calibrated with the nearby PanSTARRS 
field.


GRB_name: GRB210506A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29960
SUBJECT: GRB 210506A: Swift-XRT observations
DATE:    21/05/07 16:56:53 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J. D. Gropp (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P.
Beardmore (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB), M.G. Bernardini (INAF-OAB), A. Tohuvavohu (U. Toronto) and
P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 210506A (Aaron Tohuvavohu et al. GCN Circ.
29947), collecting 4.8 ks of Photon Counting (PC) mode data between
T0+29.0 ks and T0+45.6 ks. 

Three uncatalogued X-ray sources have been detected consistent with
being within 296 arcsec of the Swift/BAT position, however none of them
is above the RASS limit or shows definitive signs of fading. Therefore,
at the present time we cannot identify which, if any, is the afterglow.
Details of these sources are given below:

Source 3:
  RA (J2000):  132.9074  =  08:51:37.78
  Dec (J2000): +4.5999  =  +04:35:59.6
  Error: 6.4 arcsec (radius, 90% conf.)
  Count-rate: (1.46 [+0.89, -0.69])e-3 ct s^-1  
  Distance: 206 arcsec from Swift/BAT position.

Source 8:
  RA (J2000):  132.8470  =  08:51:23.29
  Dec (J2000): +4.6632  =  +04:39:47.4
  Error: 7.4 arcsec (radius, 90% conf.)
  Count-rate: (1.72 [+1.01, -0.78])e-3 ct s^-1  
  Distance: 291 arcsec from Swift/BAT position.
  Flux: (1.05 [+0.62, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 9:
  RA (J2000):  132.7917  =  08:51:10.02
  Dec (J2000): +4.6042  =  +04:36:15.2
  Error: 7.9 arcsec (radius, 90% conf.)
  Count-rate: (1.76 [+0.96, -0.76])e-3 ct s^-1  
  Distance: 232 arcsec from Swift/BAT position.
  Flux: (2.8 [+1.5, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Six uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021430.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210507A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29963
SUBJECT: GRB 210507A: Fermi GBM Final Real-time Localization
DATE:    21/05/07 18:51:02 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 18:40:38 UT on 7 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210507A (trigger 642105643.041502 / 210507778).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 285.9, Dec = -7.5 (J2000 degrees, equivalent to J2000 19h 03m, -7d 30'), with a statistical uncertainty of 4.8 degrees.

The angle from the Fermi LAT boresight is 60.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210507778/quicklook/glg_skymap_all_bn210507778.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210507778/quicklook/glg_healpix_all_bn210507778.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210507778/quicklook/glg_lc_medres34_bn210507778.gif


GRB_name: GRB210507A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29966
SUBJECT: Fermi GRB 210507A: Global MASTER-Net observations report 
DATE:    21/05/07 23:47:04 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210507A ( Fermi GBM team, GCN 29963) errorbox  13215 sec after notice time and 13259 sec after trigger time at 2021-05-07 22:21:37 UT, with upper limit up to  16.4 mag. The observations began at zenith distance = 64 deg. The sun  altitude  is -28.2 deg. 

The galactic latitude b = -7 deg., longitude l = 28 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1608957

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   13289 | 2021-05-07 22:21:37 |      MASTER-Tavrida | (18h 39m 42.53s , -05d 50m 35.3s) |   C |    60 | 16.2 |        
   13369 | 2021-05-07 22:22:56 |      MASTER-Tavrida | (18h 47m 41.85s , -05d 49m 21.3s) |   C |    60 | 15.5 |        
   13448 | 2021-05-07 22:24:16 |      MASTER-Tavrida | (19h 08m 22.09s , -03d 50m 07.2s) |   C |    60 | 14.7 |        
   14144 | 2021-05-07 22:35:52 |      MASTER-Tavrida | (18h 50m 06.67s , -11d 49m 27.8s) |   C |    60 | 14.6 |        
   14303 | 2021-05-07 22:38:31 |      MASTER-Tavrida | (18h 39m 36.28s , -05d 51m 08.3s) |   C |    60 | 16.2 |        
   14383 | 2021-05-07 22:39:50 |      MASTER-Tavrida | (18h 47m 43.48s , -05d 51m 16.2s) |   C |    60 | 15.3 |        
   14462 | 2021-05-07 22:41:10 |      MASTER-Tavrida | (19h 08m 18.97s , -03d 50m 08.6s) |   C |    60 | 16.3 |        
   14542 | 2021-05-07 22:42:29 |      MASTER-Tavrida | (19h 16m 19.74s , -03d 52m 03.0s) |   C |    60 | 15.4 |        
   14780 | 2021-05-07 22:46:27 |      MASTER-Tavrida | (18h 50m 17.91s , -01d 50m 21.3s) |   C |    60 | 16.0 |        
   14859 | 2021-05-07 22:47:47 |      MASTER-Tavrida | (18h 58m 10.12s , -01d 51m 34.0s) |   C |    60 | 15.8 |        
   14939 | 2021-05-07 22:49:06 |      MASTER-Tavrida | (18h 58m 23.62s , -11d 51m 16.5s) |   C |    60 | 15.7 |        
   15018 | 2021-05-07 22:50:25 |      MASTER-Tavrida | (18h 42m 01.11s , -11d 49m 36.3s) |   C |    60 | 16.1 |        
   15097 | 2021-05-07 22:51:45 |      MASTER-Tavrida | (18h 50m 11.34s , -11d 51m 18.5s) |   C |    60 | 15.7 |        
   15176 | 2021-05-07 22:53:04 |      MASTER-Tavrida | (19h 06m 35.40s , -11d 50m 01.0s) |   C |    60 | 15.2 |        
   15256 | 2021-05-07 22:54:23 |      MASTER-Tavrida | (18h 39m 36.53s , -05d 50m 17.3s) |   C |    60 | 15.9 |        
   15335 | 2021-05-07 22:55:43 |      MASTER-Tavrida | (18h 47m 39.14s , -05d 49m 27.6s) |   C |    60 | 15.7 |        
   15414 | 2021-05-07 22:57:02 |      MASTER-Tavrida | (19h 08m 21.68s , -03d 50m 54.0s) |   C |    60 | 16.4 |        
   15494 | 2021-05-07 22:58:21 |      MASTER-Tavrida | (19h 16m 17.82s , -03d 52m 06.1s) |   C |    60 | 16.2 |        
   15573 | 2021-05-07 22:59:40 |      MASTER-Tavrida | (19h 16m 48.78s , -07d 51m 55.6s) |   C |    60 | 14.8 |        
   16375 | 2021-05-07 23:13:02 |      MASTER-Tavrida | (19h 24m 47.14s , -07d 52m 30.5s) |   C |    60 | 15.3 |        
   16454 | 2021-05-07 23:14:21 |      MASTER-Tavrida | (18h 50m 17.29s , -01d 51m 11.9s) |   C |    60 | 16.0 |        
   16533 | 2021-05-07 23:15:41 |      MASTER-Tavrida | (18h 58m 14.20s , -01d 50m 10.2s) |   C |    60 | 15.4 |        
   16692 | 2021-05-07 23:18:20 |      MASTER-Tavrida | (18h 50m 14.77s , -11d 50m 29.4s) |   C |    60 | 13.1 |        
   16772 | 2021-05-07 23:19:39 |      MASTER-Tavrida | (19h 06m 11.36s , -01d 49m 57.6s) |   C |    60 | 14.4 |        
   16988 | 2021-05-07 23:23:15 |      MASTER-Tavrida | (19h 14m 13.03s , -01d 50m 13.9s) |   C |    60 | 13.6 |        
   17067 | 2021-05-07 23:24:35 |      MASTER-Tavrida | (18h 42m 39.27s , -09d 50m 57.9s) |   C |    60 | 14.0 |        
   17286 | 2021-05-07 23:28:13 |      MASTER-Tavrida | (19h 14m 49.76s , -11d 51m 33.2s) |   C |    60 | 12.4 |        
   17365 | 2021-05-07 23:29:33 |      MASTER-Tavrida | (18h 44m 14.43s , -03d 51m 43.4s) |   C |    60 | 15.2 |        
   17603 | 2021-05-07 23:33:31 |      MASTER-Tavrida | (18h 50m 17.03s , -01d 49m 55.9s) |   C |    60 | 14.4 |        
   17682 | 2021-05-07 23:34:50 |      MASTER-Tavrida | (18h 58m 12.28s , -01d 50m 56.9s) |   C |    60 | 14.6 |        
   17841 | 2021-05-07 23:37:29 |      MASTER-Tavrida | (19h 06m 18.59s , -01d 51m 08.0s) |   C |    60 | 14.4 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210506A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29968
SUBJECT: IPN triangulation of GRB 210506A
DATE:    21/05/08 22:49:09 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

S. Xiao, S. L. Xiong, X. B. Li, Y. Huang, and S. N. Zhang,
on behalf of the Insight-HXMT team, report:

The short-duration GRB 210506A
(Swift/BAT-GUANO detection: Tohuvavohu et al., GCN Circ. 29947)
was detected by Swift (BAT), INTEGRAL (SPI-ACS), Insight-HXMT (HE),
and Konus-Wind at about 2388 s UT (00:39:48).

We have triangulated it to a preliminary, error box
whose coordinates are:
  ------------------------------------
   RA(2000), deg       Dec(2000), deg
  ------------------------------------
  Corners:
     224.231           -32.736
     175.778           -26.218
     177.243           -30.663
     225.586           -36.393
  ------------------------------------
The error box area is about 160 sq. deg, and its maximum
dimension is 43 deg (the minimum one is 3.7 deg).
The Sun distance was 93 deg.

This box may be improved.

The IPN box is consistent with the Fermi-GBM nondetection,
inconsistent with the BAT-GUANO localization, and
is outside the BAT coded FoV.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210506_T02388/IPN/


GRB_name: GRB210506A
Detection_method: retraction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29969
SUBJECT: GRB 210506A: Swift/BAT-GUANO position retraction
DATE:    21/05/08 23:04:45 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), Jamie A. Kennea
(PSU) report:

As stated in the detection circular (GCN 29947) the candidate position
reported was uncertain, with a near-threshold significance and an
implied spectral index outside of typical astrophysical priors for GRB
prompt emission.

Without an independent spectral measurement of this burst, the BAT
candidate image-domain arcmin localization cannot be ruled out via BAT
analysis alone. However, the IPN localization (GCN 29968; which
utilizes the BAT-GUANO rates-domain detection) strongly suggests that
the GRB originated from outside the BAT FoV. An origin for the GRB
counts from along this line of sight implies a much more reasonable
(though still hard) emission spectrum.
The BAT-GUANO rates-domain detection of this GRB remains robust and we
are confident that the counts in the detector originate from GRB
210506A.

The BAT maximum likelihood analysis (DeLaunay et al. 2021, in prep)
independently shows a slight preference for an out of FoV origin. We
did not report the test statistic results for this source from the
maximum likelihood analysis in the detection circular due to delayed
run times on the cluster.

We do not identify any detector glitches, noise sources, or cosmic ray
induced showers that can account for the image source.

We conclude that the SNR 6.8 image source reported is likely to be
rare high-significance spurious image noise caused by an unfortunate
spatial correlation of true GRB counts in the detector plane.

The False Alarm Probability for a BAT source at SNR 6.8 in a
background subtracted image from ground analysis is low (~1-5%) and we
stress that other GRBs with lower image significance GUANO
localizations have been confirmed by XRT afterglow discovery.


GRB_name: GRB210509A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29970
SUBJECT: GRB 210509A: Swift detection of a burst
DATE:    21/05/09 14:45:48 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

K. L. Page (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC) and D. M. Palmer (LANL) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 14:32:20 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a GRB 210509A (trigger= 1047531).  Swift did not slew immediately
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 350.352, +6.675 which is 
  RA(J2000) = 23h 21m 25s
  Dec(J2000) = +06d 40' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Due to telemetry limitations, no further
BAT data will be available until the ground-station pass data
has been processed. 

Due to an observing constraint, Swift will not slew until T0+50
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210509A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29971
SUBJECT: GRB 210509A: Swift-XRT observations
DATE:    21/05/09 16:06:58 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows
(PSU), J.A. Kennea (PSU), M. Perri (SSDC & INAF-OAR) and G. Tagliaferri
(INAF-OAB) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 210509A at 15:45:53.0 UT,
4412.6 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 350.37430, 6.67134
which is equivalent to:
   RA(J2000)  = 23h 21m 29.83s
   Dec(J2000) = +06d 40' 16.8"
with an uncertainty of 4.4 arcseconds (radius, 90% containment). This
location is 80 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 7.11
x 10^20 cm^-2 (Willingale et al. 2013). 


GRB_name: GRB210509A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29972
SUBJECT: GRB 210509A: BOOTES-4/MET optical upper limit
DATE:    21/05/09 22:07:09 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

T.-R. Sun, Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210509A by Swift (Page et al. GCNC 29970), we triggered the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) starting on May 9 at 19:32 UT (~5 hr after trigger) with non-optimal conditions (passing clouds and the target being at high airmass). No optical source is detected at the position reported by Swift-XRT (Evans et al. GCNC 29971) down to 17.2 mag in the co-added image (clear filter). Additional observations are ongoing.

We thank the staff at Lijiang observatory for their excellent support.


GRB_name: GRB210509A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29973
SUBJECT: GRB 210509A: Enhanced Swift-XRT position
DATE:    21/05/10 01:13:40 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1722 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 210509A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 350.37564, +6.67126 which is equivalent
to:

RA (J2000): 23h 21m 30.15s
Dec (J2000): +06d 40' 16.5"

with an uncertainty of 2.5 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210509A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29974
SUBJECT: Swift GRB 210509A: Global MASTER-Net observations report 
DATE:    21/05/10 02:23:02 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210509A ( K. L. Page et al., GCN 29970) errorbox  41751 sec after notice time and 41820 sec after trigger time at 2021-05-10 02:09:20 UT, with upper limit up to  16.0 mag. The observations began at zenith distance = 77 deg. The sun  altitude  is -39.8 deg. 

The galactic latitude b = -50 deg., longitude l = 88 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1610042

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   41910 |         MASTER-SAAO |   C |   180 | 16.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210509A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29975
SUBJECT: GRB 210509A: Swift-BAT refined analysis
DATE:    21/05/10 04:33:00 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210509A (trigger #1047531)
(Page et al., GCN Circ. 29970).  The BAT ground-calculated position is
RA, Dec = 350.363, 6.650 deg which is
   RA(J2000)  =  23h 21m 27.2s
   Dec(J2000) = +06d 39' 01.1"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 95%.

The mask-weighted light curve shows several overlapping pulses that
start at ~T-2 s and end at ~T+8 s. The burst went out of the BAT FOV
at ~T+77 s. T90 (15-350 keV) is 8.22 +- 0.75 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.65 to T+7.63 sec is best fit by
a power law with an exponential cutoff.  This fit gives a photon
index 0.76 +- 1.00, and Epeak of 33.0 +- 8.3 keV (chi squared 70.16
for 56 d.o.f.).  For this model the total fluence in the 15-150 keV band
is 3.1 +- 0.4 x 10^-7 erg/cm2 and the 1-sec peak flux measured from
T+3.24 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec.  A fit to
a simple power law gives a photon index of 2.18 +- 0.17 (chi squared
78.23 for 57 d.o.f.).  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1047531/BA/


GRB_name: GRB210509A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29977
SUBJECT: GRB 210509A: Swift-XRT refined Analysis
DATE:    21/05/10 08:38:51 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), P. D'Avanzo (INAF-OAB), M.G.
Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , A. Tohuvavohu (U.
Toronto), B. Sbarufatti (PSU) and K.L. Page report on behalf of the
Swift-XRT team:

We have analysed 7.2 ks of XRT data for GRB 210509A (Page et al. GCN
Circ. 29970), from 3.2 ks to 56.6 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Goad et al. (GCN Circ. 29973).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.11 (+0.20, -0.17).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.63 (+0.36, -0.16). The
best-fitting absorption column is  consistent with the Galactic value
of 7.1 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.0 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      7.1 (+/-8.9) x 10^20 cm^-2
Galactic foreground: 7.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.63 (+0.36, -0.16)

If the light curve continues to decay with a power-law decay index of
1.11, the count rate at T+24 hours will be 2.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.7 x
10^-14 (9.6 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01047531.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210509A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29978
SUBJECT: GRB 210509A: Swift/UVOT Upper Limits
DATE:    21/05/10 10:10:56 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210509A
3202 s after the BAT trigger (Page et al., GCN Circ. 29970).
No optical afterglow consistent with the XRT position (Evans et al.
GCN Circ. 29971) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3202         3352          147         >20.8
white             3202         4585          344         >21.0
v                 3358         4934          332         >19.0
b                 4180         4380          197         >19.5
u                 3974         4174          197         >19.6
w1                3769         3969          197         >19.5
m2                3563         3763          197         >20.3
w2                4592         4792          197         >19.6

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.074 in the direction of
the burst (Schlegel et al. 1998).


GRB_name: GRB210509A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29979
SUBJECT: GRB 210509A: RATIR Optical and NIR Upper Limits 
DATE:    21/05/10 14:11:26 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H.
Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska
(UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora Troja (GSFC), Owen
Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), JesÃºs GonzÃ¡lez (UNAM), Carlos
RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou
(U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210509A (Page et al., GCN Circ. 29970) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson
Telescope at the Observatorio AstronÃ³mico Nacional on Sierra San Pedro MÃ¡rtir
from 2021/05 10.47 to 2021/05 10.48 UTC (19.34 to 19.70 hours after the BAT
trigger), obtaining a total of 0.21 hours exposure in the r and i bands and 0.08
hours exposure in the Z, Y, J, and H bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS DR9
and 2MASS catalogs, we obtain the following upper limits (3-sigma):

  r > 21.28
  i > 21.09
  Z > 18.17
  Y > 19.19
  J > 19.57
  H > 17.30

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.


GRB_name: GRB210510A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29981
SUBJECT: GRB 210510A: Fermi GBM Final Real-time Localization
DATE:    21/05/10 19:30:27 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 19:20:00 UT on 10 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210510A (trigger 642367205.830352 / 210510806).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 192.3, Dec = 44.9 (J2000 degrees, equivalent to J2000 12h 49m, 44d 53'), with a statistical uncertainty of 21.7 degrees.

The angle from the Fermi LAT boresight is 20.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210510806/quicklook/glg_skymap_all_bn210510806.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210510806/quicklook/glg_healpix_all_bn210510806.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210510806/quicklook/glg_lc_medres34_bn210510806.gif


GRB_name: GRB200716A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29984
SUBJECT: GRB 200716A: Swift/BAT-GUANO archival detection and arcminute localization
DATE:    21/05/10 21:02:08 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea
(PSU) report:

Swift/BAT did not trigger on GRB 200716A (T0: 2020-07-16 01:26:37.76
UTC),  Fermi/GBM team (GCNs 28109, 28120), BALROG (GCN 28112), AGILE
(GCN 28116), AstroSat CZTI (GCN 28117), IPN (GCN 28121).

The Fermi/GBM notice, distributed in near real-time, triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is detected in BAT with a duration of at least 60 seconds.

This burst was not localized in our low-latency analysis at the time.
An updated and improved version of the targeted search pipeline was
recently re-run on archival data and this burst was recovered.

With a maximum likelihood analysis (DeLaunay et al. 2021, in prep.) on
the event-mode data we detect a location for the burst with a square
root of the test statistic, sqrt(TS), of 110.96. The sqrt(TS) behaves
similarly to SNR.
Using the normal BAT imaging technique, we find the same location for
the GRB with an SNR of 8.5.

The partial coding fraction for this burst was 1%.  The SNR in the
image is significantly lower than the sqrt(TS) as the maximum
likelihood analysis is capable of considering counts from the burst
deposited on the detector that arrive via lines of sight that do not
pass through the coded mask. For the case of bursts at low partial
coding fractions, this yields a substantial sensitivity improvement
over imaging.

The BAT position is
RA, Dec = 139.348, -16.712 deg which is
   RA(J2000)  = 09h 17m 23.5s
   Dec(J2000) =  -16d 42â€² 43.2â€³
with an estimated uncertainty of 5 arcmin.

This position is consistent with the ~1/2 square degree IPN
localization (GCN 28121).

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/


GRB_name: GRB201228B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29985
SUBJECT: GRB 201228B: Swift/BAT-GUANO archival detection and arcminute localization
DATE:    21/05/10 21:03:44 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea
(PSU) report:

Swift/BAT did not trigger on GRB 201228B (T0: 2020-12-28 15:21:45 UTC,
Fermi/GBM trigger num 630861710, GCN 29188).

The Fermi/GBM notice, distributed in near real-time, triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is detected in BAT with a duration of ~16 seconds.

This burst was not localized in our low-latency analysis at the time.
An updated and improved version of the targeted search pipeline was
recently re-run on archival data and this burst was recovered.

With a maximum likelihood analysis (DeLaunay et al. 2021, in prep.) on
the event-mode data we detect a location for the burst with a square
root of the test statistic, sqrt(TS), of 27.88. The sqrt(TS) behaves
similarly to SNR.
Using the normal BAT imaging technique, we find the same location for
the GRB with an SNR of 13.1.

The BAT position is
RA, Dec = 35.594, 56.015 deg which is
   RA(J2000)  = 02h 22m 22.56s
   Dec(J2000) =  +56d 00â€² 54.0â€³
with an estimated uncertainty of 3 arcmin.


This position is consistent with the Fermi GBM team localization (GCN 29188).

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/


GRB_name: GRB210510A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29986
SUBJECT: Fermi GRB 210510A: Global MASTER-Net observations report 
DATE:    21/05/10 21:17:39 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210510A ( Fermi GBM team, GCN 29981) errorbox  195 sec after notice time and 624 sec after trigger time at 2021-05-10 19:30:25 UT, with upper limit up to  19.4 mag. The observations began at zenith distance =  9 deg. The sun  altitude  is -21.6 deg. 

MASTER-SAAO robotic telescope  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210510A errorbox  266 sec after notice time and 695 sec after trigger time at 2021-05-10 19:31:35 UT, with upper limit up to  19.8 mag. The observations began at zenith distance = 71 deg. The sun  altitude  is -46.4 deg. 

The galactic latitude b = 73 deg., longitude l = 123 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1610677

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     655 | 2021-05-10 19:30:25 |      MASTER-Tavrida | (12h 43m 26.49s , +35d 16m 46.0s) |   C |    60 | 18.8 |        
     725 | 2021-05-10 19:31:35 |         MASTER-SAAO | (12h 47m 18.36s , +38d 00m 12.5s) |   C |    60 | 18.6 |        
     734 | 2021-05-10 19:31:45 |      MASTER-Tavrida | (12h 53m 14.67s , +35d 15m 53.1s) |   C |    60 | 18.8 |        
     805 | 2021-05-10 19:32:55 |         MASTER-SAAO | (12h 57m 28.18s , +38d 00m 18.3s) |   C |    60 | 18.6 |        
     885 | 2021-05-10 19:34:15 |         MASTER-SAAO | (13h 06m 45.94s , +36d 00m 19.6s) |   C |    60 | 18.9 |        
     964 | 2021-05-10 19:35:35 |         MASTER-SAAO | (13h 16m 36.57s , +36d 01m 37.0s) |   C |    60 | 19.3 |        
    1016 | 2021-05-10 19:36:26 |      MASTER-Tavrida | (12h 53m 48.53s , +33d 17m 50.4s) |   C |    60 | 18.9 |        
    1044 | 2021-05-10 19:36:54 |         MASTER-SAAO | (12h 48m 34.07s , +40d 02m 32.9s) |   C |    60 | 18.7 |        
    1095 | 2021-05-10 19:37:46 |      MASTER-Tavrida | (13h 03m 42.88s , +37d 15m 57.1s) |   C |    60 | 19.0 |        
    1124 | 2021-05-10 19:38:14 |         MASTER-SAAO | (12h 59m 01.24s , +40d 01m 19.0s) |   C |    60 | 18.7 |        
    1203 | 2021-05-10 19:39:34 |         MASTER-SAAO | (13h 07m 07.94s , +34d 00m 18.1s) |   C |    60 | 19.2 |        
    1264 | 2021-05-10 19:40:34 |      MASTER-Tavrida | (13h 13m 58.18s , +37d 17m 44.8s) |   C |    60 | 19.0 |        
    1283 | 2021-05-10 19:40:53 |         MASTER-SAAO | (13h 16m 39.04s , +34d 01m 47.2s) |   C |    60 | 19.2 |        
    1343 | 2021-05-10 19:41:54 |      MASTER-Tavrida | (12h 45m 55.92s , +31d 17m 02.9s) |   C |    60 | 18.9 |        
    1363 | 2021-05-10 19:42:13 |         MASTER-SAAO | (13h 09m 23.60s , +40d 02m 05.4s) |   C |    60 | 18.6 |        
    1442 | 2021-05-10 19:43:33 |         MASTER-SAAO | (13h 19m 36.73s , +40d 00m 54.1s) |   C |    60 | 18.6 |        
    1522 | 2021-05-10 19:44:52 |         MASTER-SAAO | (12h 27m 44.76s , +36d 02m 15.7s) |   C |    60 | 19.3 |        
    1602 | 2021-05-10 19:46:12 |         MASTER-SAAO | (12h 37m 29.23s , +36d 01m 02.4s) |   C |    60 | 19.1 |        
    1681 | 2021-05-10 19:47:32 |         MASTER-SAAO | (12h 47m 36.34s , +38d 01m 14.7s) |   C |    60 | 19.0 |        
    1712 | 2021-05-10 19:48:02 |      MASTER-Tavrida | (12h 55m 27.65s , +31d 16m 34.4s) |   C |    60 | 18.5 |        
    1761 | 2021-05-10 19:48:51 |         MASTER-SAAO | (12h 57m 37.99s , +38d 02m 36.3s) |   C |    60 | 18.8 |        
    1841 | 2021-05-10 19:50:11 |         MASTER-SAAO | (13h 06m 57.68s , +36d 00m 30.6s) |   C |    60 | 19.1 |        
    1884 | 2021-05-10 19:50:54 |      MASTER-Tavrida | (12h 43m 26.25s , +35d 15m 30.1s) |   C |    60 | 18.6 |        
    1921 | 2021-05-10 19:51:31 |         MASTER-SAAO | (13h 16m 49.60s , +36d 01m 41.1s) |   C |    60 | 19.3 |        
    1963 | 2021-05-10 19:52:14 |      MASTER-Tavrida | (12h 53m 15.75s , +35d 17m 03.0s) |   C |    60 | 18.6 |        
    2001 | 2021-05-10 19:52:51 |         MASTER-SAAO | (12h 48m 46.44s , +40d 01m 58.7s) |   C |    60 | 19.0 |        
    2043 | 2021-05-10 19:53:33 |      MASTER-Tavrida | (12h 44m 11.06s , +33d 15m 16.8s) |   C |    60 | 18.6 |        
    2080 | 2021-05-10 19:54:11 |         MASTER-SAAO | (12h 59m 07.35s , +40d 02m 43.5s) |   C |    60 | 18.9 |        
    2122 | 2021-05-10 19:54:52 |      MASTER-Tavrida | (12h 53m 54.03s , +33d 16m 51.5s) |   C |    60 | 18.7 |        
    2160 | 2021-05-10 19:55:30 |         MASTER-SAAO | (13h 07m 18.49s , +34d 01m 23.8s) |   C |    60 | 19.4 |        
    2240 | 2021-05-10 19:56:50 |         MASTER-SAAO | (13h 16m 47.58s , +34d 00m 09.2s) |   C |    60 | 19.3 |        
    2319 | 2021-05-10 19:58:10 |         MASTER-SAAO | (13h 09m 35.11s , +40d 00m 34.7s) |   C |    60 | 18.8 |        
    2399 | 2021-05-10 19:59:30 |         MASTER-SAAO | (13h 19m 52.79s , +40d 02m 10.9s) |   C |    60 | 18.9 |        
    2451 | 2021-05-10 20:00:21 |      MASTER-Tavrida | (13h 07m 43.98s , +39d 06m 51.0s) |   C |    60 | 19.2 |        
    2479 | 2021-05-10 20:00:49 |         MASTER-SAAO | (12h 27m 49.38s , +36d 01m 47.5s) |   C |    60 | 19.4 |        
    2560 | 2021-05-10 20:02:10 |         MASTER-SAAO | (12h 37m 43.47s , +36d 03m 21.7s) |   C |    60 | 19.1 |        
    2639 | 2021-05-10 20:03:30 |         MASTER-SAAO | (12h 27m 28.23s , +38d 03m 48.9s) |   C |    60 | 19.4 |        
    2719 | 2021-05-10 20:04:49 |         MASTER-SAAO | (12h 47m 46.61s , +38d 02m 16.7s) |   C |    60 | 19.4 |        
    2798 | 2021-05-10 20:06:09 |         MASTER-SAAO | (12h 37m 35.89s , +38d 01m 36.0s) |   C |    60 | 19.2 |        
    2822 | 2021-05-10 20:06:32 |      MASTER-Tavrida | (13h 13m 54.97s , +37d 17m 13.2s) |   C |    60 | 19.0 |        
    2878 | 2021-05-10 20:07:28 |         MASTER-SAAO | (12h 57m 52.50s , +38d 01m 10.9s) |   C |    60 | 19.3 |        
    2901 | 2021-05-10 20:07:51 |      MASTER-Tavrida | (12h 45m 56.80s , +31d 15m 37.7s) |   C |    60 | 19.1 |        
    2958 | 2021-05-10 20:08:48 |         MASTER-SAAO | (13h 07m 09.82s , +36d 02m 38.8s) |   C |    60 | 19.2 |        
    3037 | 2021-05-10 20:10:08 |         MASTER-SAAO | (13h 16m 58.47s , +36d 00m 45.7s) |   C |    60 | 19.3 |        
    3073 | 2021-05-10 20:10:43 |      MASTER-Tavrida | (12h 55m 21.49s , +31d 15m 21.2s) |   C |    60 | 18.7 |        
    3117 | 2021-05-10 20:11:27 |         MASTER-SAAO | (12h 49m 02.96s , +40d 03m 10.9s) |   C |    60 | 19.3 |        
    3153 | 2021-05-10 20:12:03 |      MASTER-Tavrida | (12h 34m 28.11s , +33d 16m 18.8s) |   C |    60 | 19.0 |        
    3197 | 2021-05-10 20:12:47 |         MASTER-SAAO | (12h 59m 17.74s , +40d 02m 10.5s) |   C |    60 | 18.8 |        
    3323 | 2021-05-10 20:14:54 |      MASTER-Tavrida | (12h 43m 20.26s , +35d 16m 17.4s) |   C |    60 | 18.9 |        
    3403 | 2021-05-10 20:16:13 |      MASTER-Tavrida | (12h 53m 09.24s , +35d 15m 41.6s) |   C |    60 | 19.0 |        
    3482 | 2021-05-10 20:17:33 |      MASTER-Tavrida | (12h 44m 04.78s , +33d 16m 26.5s) |   C |    60 | 19.0 |        
    3516 | 2021-05-10 20:18:07 |         MASTER-SAAO | (13h 07m 32.69s , +34d 01m 38.5s) |   C |    60 | 19.2 |        
    3562 | 2021-05-10 20:18:52 |      MASTER-Tavrida | (12h 53m 50.63s , +33d 15m 35.1s) |   C |    60 | 18.9 |        
    3596 | 2021-05-10 20:19:26 |         MASTER-SAAO | (13h 17m 01.23s , +34d 00m 27.0s) |   C |    60 | 19.3 |        
    3641 | 2021-05-10 20:20:11 |      MASTER-Tavrida | (13h 03m 39.09s , +37d 14m 44.9s) |   C |    60 | 19.2 |        
    3676 | 2021-05-10 20:20:46 |         MASTER-SAAO | (13h 09m 50.95s , +40d 00m 53.9s) |   C |    60 | 19.0 |        
    3756 | 2021-05-10 20:22:06 |         MASTER-SAAO | (13h 20m 09.64s , +40d 02m 16.0s) |   C |    60 | 18.9 |        
    3812 | 2021-05-10 20:23:02 |      MASTER-Tavrida | (12h 24m 46.52s , +33d 15m 54.2s) |   C |    60 | 18.8 |        
    3836 | 2021-05-10 20:23:26 |         MASTER-SAAO | (12h 27m 56.26s , +36d 02m 20.8s) |   C |    60 | 19.3 |        
    3891 | 2021-05-10 20:24:22 |      MASTER-Tavrida | (13h 13m 51.39s , +37d 14m 55.6s) |   C |    60 | 19.3 |        
    3915 | 2021-05-10 20:24:46 |         MASTER-SAAO | (12h 37m 50.22s , +36d 03m 41.6s) |   C |    60 | 19.2 |        
    3971 | 2021-05-10 20:25:41 |      MASTER-Tavrida | (12h 45m 53.47s , +31d 15m 59.7s) |   C |    60 | 19.1 |        
    3995 | 2021-05-10 20:26:05 |         MASTER-SAAO | (12h 27m 35.56s , +38d 03m 23.6s) |   C |    60 | 19.4 |        
    4050 | 2021-05-10 20:27:01 |      MASTER-Tavrida | (12h 55m 13.37s , +31d 15m 24.8s) |   C |    60 | 19.1 |        
    4075 | 2021-05-10 20:27:25 |         MASTER-SAAO | (12h 37m 43.48s , +38d 04m 08.6s) |   C |    60 | 19.4 |        
    4130 | 2021-05-10 20:28:20 |      MASTER-Tavrida | (12h 34m 23.91s , +33d 15m 57.7s) |   C |    60 | 19.0 |        
    4360 | 2021-05-10 20:32:10 |      MASTER-Tavrida | (13h 14m 08.25s , +31d 16m 37.0s) |   C |    60 | 19.4 |        
    4392 | 2021-05-10 20:32:42 |         MASTER-SAAO | (12h 46m 37.46s , +36d 01m 45.7s) |   C |    60 | 19.0 |        
    4439 | 2021-05-10 20:33:30 |      MASTER-Tavrida | (12h 43m 13.89s , +37d 14m 06.1s) |   C |    60 | 19.1 |        
    4472 | 2021-05-10 20:34:02 |         MASTER-SAAO | (12h 56m 25.63s , +36d 03m 27.9s) |   C |    60 | 19.2 |        
    4519 | 2021-05-10 20:34:49 |      MASTER-Tavrida | (12h 53m 31.29s , +37d 14m 17.2s) |   C |    60 | 19.0 |        
    4598 | 2021-05-10 20:36:09 |      MASTER-Tavrida | (13h 03m 03.01s , +35d 14m 41.9s) |   C |    60 | 19.4 |        
    4678 | 2021-05-10 20:37:28 |      MASTER-Tavrida | (13h 13m 00.49s , +35d 16m 02.5s) |   C |    60 | 17.8 |        
    4757 | 2021-05-10 20:38:48 |      MASTER-Tavrida | (12h 24m 41.38s , +33d 14m 33.5s) |   C |    60 | 18.2 |        
    4788 | 2021-05-10 20:39:19 |         MASTER-SAAO | (12h 47m 14.67s , +34d 02m 45.3s) |   C |    60 | 19.1 |        
    4837 | 2021-05-10 20:40:07 |      MASTER-Tavrida | (12h 44m 22.41s , +39d 15m 04.4s) |   C |    60 | 18.4 |        
    4868 | 2021-05-10 20:40:38 |         MASTER-SAAO | (12h 56m 52.56s , +34d 03m 34.6s) |   C |    60 | 19.2 |        
    4916 | 2021-05-10 20:41:26 |      MASTER-Tavrida | (12h 54m 43.17s , +39d 14m 13.2s) |   C |    60 | 17.7 |        
    4948 | 2021-05-10 20:41:58 |         MASTER-SAAO | (12h 26m 33.47s , +38d 03m 43.1s) |   C |    60 | 19.3 |        
    5028 | 2021-05-10 20:43:18 |         MASTER-SAAO | (12h 36m 35.41s , +38d 02m 29.3s) |   C |    60 | 19.2 |        
    5107 | 2021-05-10 20:44:38 |         MASTER-SAAO | (12h 48m 57.58s , +32d 03m 46.0s) |   C |    60 | 19.3 |        
    5134 | 2021-05-10 20:45:05 |      MASTER-Tavrida | (13h 13m 03.10s , +33d 16m 20.5s) |   C |    60 | 18.2 |        
    5187 | 2021-05-10 20:45:57 |         MASTER-SAAO | (12h 50m 14.37s , +42d 04m 13.2s) |   C |    60 | 19.3 |        
    5214 | 2021-05-10 20:46:24 |      MASTER-Tavrida | (12h 34m 26.73s , +33d 14m 33.4s) |   C |    60 | 18.7 |        
    5267 | 2021-05-10 20:47:17 |         MASTER-SAAO | (12h 58m 19.35s , +32d 02m 48.6s) |   C |    60 | 19.5 |        
    5294 | 2021-05-10 20:47:44 |      MASTER-Tavrida | (13h 04m 38.97s , +31d 14m 04.4s) |   C |    60 | 18.7 |        
    5346 | 2021-05-10 20:48:37 |         MASTER-SAAO | (13h 00m 52.63s , +42d 03m 59.6s) |   C |    60 | 19.3 |        
    5373 | 2021-05-10 20:49:03 |      MASTER-Tavrida | (13h 14m 12.99s , +31d 14m 27.2s) |   C |    60 | 19.1 |        
    5426 | 2021-05-10 20:49:56 |         MASTER-SAAO | (12h 46m 39.77s , +36d 03m 23.4s) |   C |    60 | 19.3 |        
    5452 | 2021-05-10 20:50:22 |      MASTER-Tavrida | (12h 43m 16.29s , +37d 15m 37.9s) |   C |    60 | 18.3 |        
    5505 | 2021-05-10 20:51:16 |         MASTER-SAAO | (12h 56m 26.46s , +36d 02m 06.8s) |   C |    60 | 19.4 |        
    5532 | 2021-05-10 20:51:42 |      MASTER-Tavrida | (12h 53m 26.95s , +37d 14m 07.7s) |   C |    60 | 18.7 |        
    5585 | 2021-05-10 20:52:35 |         MASTER-SAAO | (12h 27m 06.57s , +40d 04m 48.3s) |   C |    60 | 19.4 |        
    5611 | 2021-05-10 20:53:01 |      MASTER-Tavrida | (13h 03m 05.20s , +35d 15m 46.0s) |   C |    60 | 18.2 |        
    5665 | 2021-05-10 20:53:55 |         MASTER-SAAO | (12h 37m 33.27s , +40d 02m 58.9s) |   C |    60 | 19.2 |        
    5690 | 2021-05-10 20:54:21 |      MASTER-Tavrida | (13h 12m 53.41s , +35d 15m 06.8s) |   C |    60 | 18.2 |        
    5744 | 2021-05-10 20:55:14 |         MASTER-SAAO | (12h 47m 26.03s , +34d 04m 23.3s) |   C |    60 | 19.4 |        
    5770 | 2021-05-10 20:55:40 |      MASTER-Tavrida | (12h 44m 13.37s , +39d 15m 41.7s) |   C |    60 | 18.1 |        
    5824 | 2021-05-10 20:56:34 |         MASTER-SAAO | (12h 56m 57.67s , +34d 03m 13.2s) |   C |    60 | 19.3 |        
    5904 | 2021-05-10 20:57:54 |         MASTER-SAAO | (12h 28m 44.20s , +42d 04m 20.3s) |   C |    60 | 19.2 |        
    5922 | 2021-05-10 20:58:13 |      MASTER-Tavrida | (13h 03m 21.98s , +33d 13m 49.1s) |   C |    60 | 19.2 |        
    5983 | 2021-05-10 20:59:14 |         MASTER-SAAO | (12h 39m 24.28s , +42d 03m 02.3s) |   C |    60 | 19.2 |        
    6063 | 2021-05-10 21:00:34 |         MASTER-SAAO | (12h 49m 04.18s , +32d 02m 40.5s) |   C |    60 | 19.5 |        
    6145 | 2021-05-10 21:01:55 |         MASTER-SAAO | (12h 50m 13.22s , +42d 04m 40.8s) |   C |    60 | 19.3 |        
    6224 | 2021-05-10 21:03:15 |         MASTER-SAAO | (12h 28m 10.66s , +34d 05m 14.3s) |   C |    60 | 19.5 |        
    6304 | 2021-05-10 21:04:35 |         MASTER-SAAO | (12h 58m 24.63s , +32d 03m 21.0s) |   C |    60 | 19.5 |        
    6384 | 2021-05-10 21:05:54 |         MASTER-SAAO | (12h 37m 43.23s , +34d 05m 09.6s) |   C |    60 | 19.3 |        
    6464 | 2021-05-10 21:07:14 |         MASTER-SAAO | (13h 01m 02.68s , +42d 03m 32.8s) |   C |    60 | 19.3 |        
    6544 | 2021-05-10 21:08:34 |         MASTER-SAAO | (12h 33m 07.87s , +30d 03m 39.9s) |   C |    60 | 19.8 |        
    6623 | 2021-05-10 21:09:54 |         MASTER-SAAO | (12h 46m 40.78s , +36d 04m 46.7s) |   C |    60 | 19.4 |        
    6703 | 2021-05-10 21:11:13 |         MASTER-SAAO | (12h 56m 33.82s , +36d 02m 43.7s) |   C |    60 | 19.4 |        
    6783 | 2021-05-10 21:12:33 |         MASTER-SAAO | (12h 27m 09.86s , +40d 05m 45.4s) |   C |    60 | 19.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210511A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29987
SUBJECT: GRB 210511A: Fermi GBM Final Real-time Localization
DATE:    21/05/11 11:09:18 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 10:58:57 UT on 11 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210511A (trigger 642423542.350354 / 210511458).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 249.3, Dec = 69.0 (J2000 degrees, equivalent to J2000 16h 37m, 69d 00'), with a statistical uncertainty of 10.5 degrees.

The angle from the Fermi LAT boresight is 34.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210511458/quicklook/glg_skymap_all_bn210511458.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210511458/quicklook/glg_healpix_all_bn210511458.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210511458/quicklook/glg_lc_medres34_bn210511458.gif


GRB_name: GRB210511B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29988
SUBJECT: GRB 210511B: Fermi GBM Final Real-time Localization
DATE:    21/05/11 11:36:59 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 11:26:39 UT on 11 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210511B (trigger 642425204.260366 / 210511477).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 316.2, Dec = 61.7 (J2000 degrees, equivalent to J2000 21h 04m, 61d 42'), with a statistical uncertainty of 1.0 degrees.

The angle from the Fermi LAT boresight is 49.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210511477/quicklook/glg_skymap_all_bn210511477.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210511477/quicklook/glg_healpix_all_bn210511477.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210511477/quicklook/glg_lc_medres34_bn210511477.gif


GRB_name: GRB210511B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29989
SUBJECT: GRB 210511B: BALROG localization (Fermi Trigger 642425204 / GRB 210511477)
DATE:    21/05/11 11:47:05 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
642425204 at 11:26:39 on 11 May 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 314.1+/-1.4 deg
Decl.(2000.0) = 56.3+/-0.6 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210511477/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210511477/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210511477/json

                        


GRB_name: GRB210511B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29990
SUBJECT: GRB 210511B: GECAM detection
DATE:    21/05/11 14:50:20 GMT
FROM:    Ce Cai at IHEP  <caice@ihep.ac.cn>

C. Cai, S. L. Xie, Y. Huang, S. L. Xiong, S. Xiao, Y. Zhao, J. C. Liu,
C. Y. Li, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, Q. B. Yi,
B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang,
K. Zhang, P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao,  S. J. Zheng,
X. Zhou (IHEP), report on behalf of GECAM team:

During the commissioning phase, GECAM-B was triggered by a long GRB 210511B
at 2021-05-11T11:26:40.600 UTC (denoted as T0), 
which was also observed by Fermi/GBM (GCN #29988).

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of 
a single pulse with a duration of about 10s.  

An automatic on-ground localization was calculated using the light curves
and spectrum. Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
ra: 317.99 deg
dec: 59.53 deg
err: 3.19 deg (statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. This position is 
consistent with the Fermi GBM team localization (GCN 29988) within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_74431600.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210511B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29991
SUBJECT: GRB 210511B: AGILE detection
DATE:    21/05/11 17:11:19 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), V. Fioretti (INAF/OAS-Bologna), M. Tavani (INAF/IAPS,
and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y.
Evangelista, G. Piano (INAF/IAPS), F. Lucarelli, C. Pittori, F. Verrecchia
(SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano,  F. Fuschino, N.
Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen
University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F.
Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:

The AGILE satellite detected the long GRB 210511B at T0 = 2021-05-11
11:26:37 s (UTC), reported by Fermi/GBM (GCN #29988) and GECAM (GCN #29990).

The burst is visible in the AGILE scientific ratemeters of the SuperAGILE
(SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and AntiCoincidence
(AC; 50-200 keV) detectors. The event lasted ~12 s and released a total
number of 2120 counts in the SA detector (above a background rate of 64
Hz), 15630 counts in the MCAL detector (above a background rate of 1260
Hz), and 48375 counts in the AC detector (above a background rate of 3865
Hz). The AGILE ratemeter light curves can be found at
http://www.agilescienceapp.it/notices/GRB210511_AGILE_RM.png .

Additional analysis of AGILE data is in progress.


GRB_name: GRB210511B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29992
SUBJECT: Fermi GRB 210511B: Global MASTER-Net observations report 
DATE:    21/05/11 18:31:20 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210511B ( Fermi GBM team, GCN 29988) errorbox  24287 sec after notice time and 24402 sec after trigger time at 2021-05-11 18:13:21 UT, with upper limit up to  18.0 mag. The observations began at zenith distance = 68 deg. The sun  altitude  is -17.1 deg. 

The galactic latitude b = 10 deg., longitude l = 99 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1611119

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   24492 | 2021-05-11 18:13:21 |   MASTER-Kislovodsk | (21h 04m 20.43s , +61d 44m 35.3s) |   C |   180 | 17.6 |        
   24493 | 2021-05-11 18:13:21 |   MASTER-Kislovodsk | (21h 04m 10.88s , +61d 20m 40.1s) |   C |   180 | 18.0 |        
   24693 | 2021-05-11 18:16:41 |   MASTER-Kislovodsk | (21h 04m 27.56s , +61d 43m 35.1s) |   C |   180 | 17.5 |        
   24693 | 2021-05-11 18:16:41 |   MASTER-Kislovodsk | (21h 04m 18.29s , +61d 19m 37.6s) |   C |   180 | 18.0 |        
   24893 | 2021-05-11 18:20:02 |   MASTER-Kislovodsk | (20h 54m 20.98s , +62d 42m 45.4s) |   C |   180 | 17.4 |        
   24893 | 2021-05-11 18:20:02 |   MASTER-Kislovodsk | (20h 54m 12.62s , +62d 18m 48.3s) |   C |   180 | 17.9 |        
   25093 | 2021-05-11 18:23:22 |   MASTER-Kislovodsk | (20h 54m 27.35s , +62d 43m 01.4s) |   C |   180 | 17.4 |        
   25093 | 2021-05-11 18:23:22 |   MASTER-Kislovodsk | (20h 54m 19.40s , +62d 19m 03.9s) |   C |   180 | 17.8 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210510A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29993
SUBJECT: Fermi GRB 210510A: DDOTI Upper Limits on the Afterglow
DATE:    21/05/11 19:55:18 GMT
FROM:    Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada  <mpereyra@astro.unam.mx>

Margarita Pereyra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM),
Eleonora Troja (GSFC/UMD),  Simone Dichiara (GSFC/UMD), Rosa L. Becerra
(UNAM), William H. Lee (UNAM), OcÃ©lotl LÃ³pez,  Diego Gonzalez (UNAM),
Alexander Kutyrev (GSFC/UMD), and Srihari Ravi (ASU), report:

We observed the field of the likely short Fermi GRB 210510A (trigger
642367205, GCN #29981, Fermi GBM Team) with the DDOTI/OAN wide-field imager
at the Observatorio AstronÃ³mico Nacional on Sierra San Pedro MÃ¡rtir (
http://ddoti.astroscu.unam.mx) on 2021-05-11 from 03:24 to 10:45 UTC (8.1
to  15.4 hours after the event).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA = 192.330,
Dec = +44.860 (J2000 degrees). This region contains 6 instrumental fields
or about 400 square degrees. We obtained 2280 to 2400 seconds of exposure
per instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.

We detect no likely candidate for the afterglow to our 10-sigma upper
limits of w = 20.20 to 20.42 (interquartile range).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210511A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29994
SUBJECT: Fermi GRB 210511A: Global MASTER-Net observations report 
DATE:    21/05/11 20:46:45 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210511A ( Fermi GBM team, GCN 29987) errorbox  31964 sec after notice time and 32072 sec after trigger time at 2021-05-11 19:53:29 UT, with upper limit up to  17.6 mag. The observations began at zenith distance = 32 deg. The sun  altitude  is -26.7 deg. 

The galactic latitude b = 37 deg., longitude l = 101 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1611078

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   17776 | 2021-05-11 15:54:43 |             MASTER- | (16h 11m 45.39s , +64d 29m 33.2s) |   C |    60 | 16.4 |        
   17919 | 2021-05-11 15:57:06 |             MASTER- | (17h 18m 28.83s , +67d 50m 42.2s) |   C |    60 | 17.0 |        
   17919 | 2021-05-11 15:57:06 |             MASTER- | (16h 58m 08.51s , +66d 35m 19.7s) |   C |    60 | 16.8 |        
   17992 | 2021-05-11 15:58:19 |             MASTER- | (16h 31m 56.69s , +66d 40m 17.0s) |   C |    60 | 18.8 |        
   17992 | 2021-05-11 15:58:19 |             MASTER- | (16h 12m 30.91s , +65d 24m 48.1s) |   C |    60 | 18.2 |        
   18191 | 2021-05-11 16:01:37 |             MASTER- | (16h 33m 14.89s , +64d 41m 58.1s) |   C |    60 | 19.2 |        
   18191 | 2021-05-11 16:01:37 |             MASTER- | (16h 15m 11.82s , +63d 26m 31.2s) |   C |    60 | 18.4 |        
   18263 | 2021-05-11 16:02:49 |             MASTER- | (15h 48m 35.16s , +68d 43m 46.2s) |   C |    60 | 19.5 |        
   18263 | 2021-05-11 16:02:49 |             MASTER- | (15h 27m 23.94s , +67d 28m 09.8s) |   C |    60 | 18.0 |        
   18337 | 2021-05-11 16:04:04 |             MASTER- | (17h 09m 56.61s , +64d 37m 41.7s) |   C |    60 | 19.1 |        
   18337 | 2021-05-11 16:04:04 |             MASTER- | (16h 51m 57.40s , +63d 22m 22.0s) |   C |    60 | 17.5 |        
   18413 | 2021-05-11 16:05:20 |             MASTER- | (15h 22m 09.67s , +69d 27m 37.0s) |   C |    60 | 18.0 |        
   18413 | 2021-05-11 16:05:20 |             MASTER- | (15h 45m 23.23s , +70d 43m 26.2s) |   C |    60 | 19.2 |        
   18484 | 2021-05-11 16:06:30 |             MASTER- | (15h 52m 14.22s , +66d 44m 40.2s) |   C |    60 | 19.4 |        
   18484 | 2021-05-11 16:06:30 |             MASTER- | (15h 32m 40.87s , +65d 28m 57.7s) |   C |    60 | 18.3 |        
   18555 | 2021-05-11 16:07:42 |             MASTER- | (15h 42m 47.54s , +72d 44m 10.5s) |   C |    60 | 19.1 |        
   18555 | 2021-05-11 16:07:42 |             MASTER- | (15h 17m 02.96s , +71d 28m 13.9s) |   C |    60 | 18.0 |        
   18627 | 2021-05-11 16:08:54 |             MASTER- | (16h 18m 46.28s , +61d 26m 47.0s) |   C |    60 | 17.9 |        
   18627 | 2021-05-11 16:08:54 |             MASTER- | (16h 35m 40.04s , +62d 42m 26.7s) |   C |    60 | 19.0 |        
   18699 | 2021-05-11 16:10:06 |             MASTER- | (15h 38m 18.51s , +63d 28m 08.1s) |   C |    60 | 18.3 |        
   18699 | 2021-05-11 16:10:06 |             MASTER- | (15h 56m 26.62s , +64d 43m 54.5s) |   C |    60 | 19.5 |        
   18775 | 2021-05-11 16:11:21 |             MASTER- | (17h 36m 33.04s , +67d 21m 33.2s) |   C |    60 | 18.1 |        
   18775 | 2021-05-11 16:11:21 |             MASTER- | (17h 57m 34.21s , +68d 37m 04.8s) |   C |    60 | 19.2 |        
   18845 | 2021-05-11 16:12:31 |             MASTER- | (17h 51m 07.40s , +66d 36m 35.4s) |   C |    60 | 19.4 |        
   18845 | 2021-05-11 16:12:31 |             MASTER- | (17h 31m 46.01s , +65d 21m 02.8s) |   C |    60 | 18.2 |        
   18921 | 2021-05-11 16:13:48 |             MASTER- | (16h 10m 22.53s , +67d 25m 29.6s) |   C |    60 | 18.3 |        
   18921 | 2021-05-11 16:13:48 |             MASTER- | (16h 31m 33.17s , +68d 41m 07.5s) |   C |    60 | 19.4 |        
   18992 | 2021-05-11 16:14:59 |             MASTER- | (16h 09m 28.03s , +69d 25m 57.0s) |   C |    60 | 18.1 |        
   18993 | 2021-05-11 16:14:59 |             MASTER- | (16h 32m 40.37s , +70d 41m 35.7s) |   C |    60 | 19.5 |        
   19064 | 2021-05-11 16:16:11 |             MASTER- | (16h 53m 31.11s , +67d 24m 31.1s) |   C |    60 | 17.8 |        
   19064 | 2021-05-11 16:16:11 |             MASTER- | (17h 14m 39.31s , +68d 40m 02.8s) |   C |    60 | 19.6 |        
   19134 | 2021-05-11 16:17:21 |             MASTER- | (17h 19m 46.86s , +70d 38m 31.7s) |   C |    60 | 19.5 |        
   19134 | 2021-05-11 16:17:21 |             MASTER- | (16h 56m 39.63s , +69d 23m 00.4s) |   C |    60 | 18.3 |        
   19207 | 2021-05-11 16:18:33 |             MASTER- | (16h 12m 24.16s , +65d 27m 19.7s) |   C |    60 | 18.2 |        
   19207 | 2021-05-11 16:18:33 |             MASTER- | (16h 31m 55.84s , +66d 42m 58.5s) |   C |    60 | 19.2 |        
   19277 | 2021-05-11 16:19:44 |             MASTER- | (16h 35m 05.25s , +72d 42m 17.5s) |   C |    60 | 19.2 |        
   19277 | 2021-05-11 16:19:44 |             MASTER- | (16h 09m 22.99s , +71d 26m 37.7s) |   C |    60 | 18.0 |        
   19349 | 2021-05-11 16:20:56 |             MASTER- | (16h 52m 56.81s , +61d 25m 11.0s) |   C |    60 | 18.1 |        
   19349 | 2021-05-11 16:20:56 |             MASTER- | (17h 09m 48.31s , +62d 40m 46.6s) |   C |    60 | 19.0 |        
   19439 | 2021-05-11 16:22:26 |             MASTER- | (16h 52m 03.49s , +65d 24m 14.4s) |   C |    60 | 18.0 |        
   19439 | 2021-05-11 16:22:26 |             MASTER- | (17h 11m 30.85s , +66d 39m 51.0s) |   C |    60 | 19.3 |        
   19511 | 2021-05-11 16:23:38 |             MASTER- | (16h 15m 03.64s , +63d 25m 32.6s) |   C |    60 | 18.3 |        
   19511 | 2021-05-11 16:23:38 |             MASTER- | (16h 33m 09.16s , +64d 41m 13.5s) |   C |    60 | 19.4 |        
   19583 | 2021-05-11 16:24:50 |             MASTER- | (15h 27m 11.67s , +67d 28m 15.1s) |   C |    60 | 18.2 |        
   19583 | 2021-05-11 16:24:50 |             MASTER- | (15h 48m 26.18s , +68d 44m 06.9s) |   C |    60 | 19.4 |        
   19658 | 2021-05-11 16:26:04 |             MASTER- | (16h 51m 52.13s , +63d 25m 19.2s) |   C |    60 | 18.1 |        
   19658 | 2021-05-11 16:26:05 |             MASTER- | (17h 09m 56.39s , +64d 40m 55.2s) |   C |    60 | 19.4 |        
   19735 | 2021-05-11 16:27:21 |             MASTER- | (15h 45m 10.72s , +70d 44m 29.6s) |   C |    60 | 19.5 |        
   19735 | 2021-05-11 16:27:21 |             MASTER- | (15h 21m 54.56s , +69d 28m 33.3s) |   C |    60 | 18.3 |        
   19805 | 2021-05-11 16:28:32 |             MASTER- | (15h 32m 33.64s , +65d 29m 37.0s) |   C |    60 | 18.5 |        
   19805 | 2021-05-11 16:28:32 |             MASTER- | (15h 52m 08.74s , +66d 45m 23.5s) |   C |    60 | 19.4 |        
   19877 | 2021-05-11 16:29:44 |             MASTER- | (15h 16m 46.10s , +71d 29m 25.3s) |   C |    60 | 17.9 |        
   19877 | 2021-05-11 16:29:44 |             MASTER- | (15h 42m 33.47s , +72d 45m 27.1s) |   C |    60 | 19.2 |        
   19949 | 2021-05-11 16:30:56 |             MASTER- | (16h 18m 31.31s , +61d 27m 46.1s) |   C |    60 | 17.8 |        
   19949 | 2021-05-11 16:30:56 |             MASTER- | (16h 35m 27.47s , +62d 43m 23.7s) |   C |    60 | 19.3 |        
   20020 | 2021-05-11 16:32:07 |             MASTER- | (15h 38m 15.71s , +63d 28m 46.0s) |   C |    60 | 18.2 |        
   20020 | 2021-05-11 16:32:07 |             MASTER- | (15h 56m 25.74s , +64d 44m 32.2s) |   C |    60 | 19.6 |        
   20099 | 2021-05-11 16:33:26 |             MASTER- | (17h 36m 25.00s , +67d 20m 44.1s) |   C |    60 | 18.3 |        
   20099 | 2021-05-11 16:33:26 |             MASTER- | (17h 57m 28.75s , +68d 36m 12.3s) |   C |    60 | 19.3 |        
   20169 | 2021-05-11 16:34:36 |             MASTER- | (17h 31m 36.49s , +65d 21m 24.4s) |   C |    60 | 18.2 |        
   20169 | 2021-05-11 16:34:36 |             MASTER- | (17h 51m 01.02s , +66d 36m 54.0s) |   C |    60 | 19.6 |        
   20356 | 2021-05-11 16:37:43 |             MASTER- | (16h 10m 18.42s , +67d 26m 47.3s) |   C |    60 | 18.6 |        
   20356 | 2021-05-11 16:37:43 |             MASTER- | (16h 31m 30.49s , +68d 42m 14.5s) |   C |    60 | 19.5 |        
   20426 | 2021-05-11 16:38:53 |             MASTER- | (16h 09m 17.23s , +69d 28m 26.3s) |   C |    60 | 18.5 |        
   20426 | 2021-05-11 16:38:53 |             MASTER- | (16h 32m 32.74s , +70d 43m 55.1s) |   C |    60 | 19.6 |        
   20497 | 2021-05-11 16:40:04 |             MASTER- | (16h 53m 22.26s , +67d 25m 21.3s) |   C |    60 | 17.9 |        
   20497 | 2021-05-11 16:40:04 |             MASTER- | (17h 14m 32.21s , +68d 40m 39.2s) |   C |    60 | 19.9 |        
   20568 | 2021-05-11 16:41:14 |             MASTER- | (16h 56m 27.77s , +69d 26m 06.6s) |   C |    60 | 18.4 |        
   20568 | 2021-05-11 16:41:14 |             MASTER- | (17h 19m 39.48s , +70d 41m 24.3s) |   C |    60 | 19.8 |        
   20644 | 2021-05-11 16:42:30 |             MASTER- | (16h 31m 50.01s , +66d 43m 15.3s) |   C |    60 | 19.3 |        
   20644 | 2021-05-11 16:42:31 |             MASTER- | (16h 12m 17.39s , +65d 27m 48.9s) |   C |    60 | 18.7 |        
   20715 | 2021-05-11 16:43:42 |             MASTER- | (16h 09m 13.08s , +71d 26m 46.7s) |   C |    60 | 18.5 |        
   20715 | 2021-05-11 16:43:42 |             MASTER- | (16h 34m 56.14s , +72d 42m 17.9s) |   C |    60 | 19.2 |        
   20787 | 2021-05-11 16:44:54 |             MASTER- | (16h 52m 57.91s , +61d 24m 39.2s) |   C |    60 | 18.1 |        
   20787 | 2021-05-11 16:44:54 |             MASTER- | (17h 09m 49.99s , +62d 40m 00.2s) |   C |    60 | 19.5 |        
   20857 | 2021-05-11 16:46:04 |             MASTER- | (17h 11m 24.67s , +66d 41m 44.8s) |   C |    60 | 19.4 |        
   20857 | 2021-05-11 16:46:04 |             MASTER- | (16h 51m 54.86s , +65d 26m 22.3s) |   C |    60 | 18.2 |        
   20928 | 2021-05-11 16:47:15 |             MASTER- | (16h 15m 00.51s , +63d 27m 01.0s) |   C |    60 | 18.4 |        
   20928 | 2021-05-11 16:47:15 |             MASTER- | (16h 33m 07.46s , +64d 42m 27.5s) |   C |    60 | 19.4 |        
   21001 | 2021-05-11 16:48:28 |             MASTER- | (15h 27m 02.80s , +67d 30m 22.9s) |   C |    60 | 18.4 |        
   21001 | 2021-05-11 16:48:28 |             MASTER- | (15h 48m 19.12s , +68d 46m 04.1s) |   C |    60 | 19.5 |        
   21077 | 2021-05-11 16:49:44 |             MASTER- | (16h 51m 43.27s , +63d 25m 49.8s) |   C |    60 | 18.1 |        
   21077 | 2021-05-11 16:49:44 |             MASTER- | (17h 09m 48.66s , +64d 41m 10.1s) |   C |    60 | 19.4 |        
   21151 | 2021-05-11 16:50:58 |             MASTER- | (15h 21m 38.82s , +69d 31m 05.3s) |   C |    60 | 18.2 |        
   21151 | 2021-05-11 16:50:58 |             MASTER- | (15h 44m 57.70s , +70d 46m 50.4s) |   C |    60 | 19.5 |        
   21221 | 2021-05-11 16:52:08 |             MASTER- | (15h 32m 24.95s , +65d 29m 55.2s) |   C |    60 | 18.4 |        
   21221 | 2021-05-11 16:52:08 |             MASTER- | (15h 52m 00.23s , +66d 45m 31.1s) |   C |    60 | 19.4 |        
   21299 | 2021-05-11 16:53:26 |             MASTER- | (15h 42m 19.18s , +72d 45m 21.3s) |   C |    60 | 19.0 |        
   21299 | 2021-05-11 16:53:26 |             MASTER- | (15h 16m 33.11s , +71d 29m 18.0s) |   C |    60 | 18.1 |        
   21372 | 2021-05-11 16:54:39 |             MASTER- | (16h 18m 29.78s , +61d 27m 18.0s) |   C |    60 | 18.2 |        
   21372 | 2021-05-11 16:54:39 |             MASTER- | (16h 35m 24.96s , +62d 42m 57.6s) |   C |    60 | 19.3 |        
   21443 | 2021-05-11 16:55:50 |             MASTER- | (15h 38m 03.34s , +63d 30m 15.4s) |   C |    60 | 18.2 |        
   21443 | 2021-05-11 16:55:50 |             MASTER- | (15h 56m 13.30s , +64d 46m 05.7s) |   C |    60 | 19.5 |        
   21522 | 2021-05-11 16:57:09 |             MASTER- | (17h 36m 20.81s , +67d 22m 20.8s) |   C |    60 | 18.5 |        
   21522 | 2021-05-11 16:57:09 |             MASTER- | (17h 57m 26.09s , +68d 37m 49.5s) |   C |    60 | 19.5 |        
   21593 | 2021-05-11 16:58:20 |             MASTER- | (17h 31m 29.69s , +65d 24m 22.8s) |   C |    60 | 18.5 |        
   21593 | 2021-05-11 16:58:20 |             MASTER- | (17h 50m 56.57s , +66d 39m 52.7s) |   C |    60 | 19.4 |        
   21777 | 2021-05-11 17:01:24 |             MASTER- | (17h 09m 39.43s , +62d 42m 42.1s) |   C |    60 | 19.4 |        
   21777 | 2021-05-11 17:01:24 |             MASTER- | (16h 52m 45.87s , +61d 27m 21.1s) |   C |    60 | 18.2 |        
   21970 | 2021-05-11 17:04:37 |             MASTER- | (16h 00m 58.37s , +62d 44m 15.4s) |   C |    60 | 19.5 |        
   21970 | 2021-05-11 17:04:37 |             MASTER- | (15h 44m 01.20s , +61d 28m 55.7s) |   C |    60 | 18.3 |        
   22315 | 2021-05-11 17:10:22 |             MASTER- | (16h 38m 37.69s , +60d 44m 31.8s) |   C |    60 | 19.4 |        
   22315 | 2021-05-11 17:10:22 |             MASTER- | (16h 22m 42.34s , +59d 29m 55.3s) |   C |    60 | 18.6 |        
   22388 | 2021-05-11 17:11:35 |             MASTER- | (17h 46m 28.84s , +64d 40m 03.5s) |   C |    60 | 19.4 |        
   22388 | 2021-05-11 17:11:35 |             MASTER- | (17h 28m 22.36s , +63d 25m 35.9s) |   C |    60 | 18.5 |        
   22459 | 2021-05-11 17:12:46 |             MASTER- | (17h 10m 42.27s , +60d 43m 08.5s) |   C |    60 | 19.3 |        
   22459 | 2021-05-11 17:12:46 |             MASTER- | (16h 54m 47.85s , +59d 28m 37.4s) |   C |    60 | 18.1 |        
   22537 | 2021-05-11 17:14:04 |             MASTER- | (17h 44m 01.34s , +62d 40m 12.0s) |   C |    60 | 19.5 |        
   22537 | 2021-05-11 17:14:04 |             MASTER- | (17h 27m 07.03s , +61d 25m 44.7s) |   C |    60 | 17.5 |        
   22730 | 2021-05-11 17:17:17 |             MASTER- | (15h 12m 02.72s , +66d 47m 20.2s) |   C |    60 | 19.2 |        
   22730 | 2021-05-11 17:17:17 |             MASTER- | (14h 52m 25.62s , +65d 32m 00.7s) |   C |    60 | 18.5 |        
   22934 | 2021-05-11 17:20:41 |             MASTER- | (15h 04m 41.95s , +68d 48m 09.5s) |   C |    60 | 19.4 |        
   22934 | 2021-05-11 17:20:41 |             MASTER- | (14h 43m 24.40s , +67d 34m 37.0s) |   C |    60 | 17.9 |        
   23004 | 2021-05-11 17:21:51 |             MASTER- | (14h 57m 20.00s , +70d 49m 40.2s) |   C |    60 | 19.5 |        
   23004 | 2021-05-11 17:21:51 |             MASTER- | (14h 34m 00.08s , +69d 35m 53.5s) |   C |    60 | 18.4 |        
   23075 | 2021-05-11 17:23:02 |             MASTER- | (15h 19m 06.76s , +64d 48m 21.5s) |   C |    60 | 19.7 |        
   23075 | 2021-05-11 17:23:02 |             MASTER- | (15h 00m 53.96s , +63d 35m 04.6s) |   C |    60 | 18.7 |        
   23149 | 2021-05-11 17:24:16 |             MASTER- | (16h 06m 09.70s , +60d 47m 39.2s) |   C |    60 | 19.4 |        
   23149 | 2021-05-11 17:24:16 |             MASTER- | (15h 50m 11.90s , +59d 34m 37.9s) |   C |    60 | 18.4 |        
   23221 | 2021-05-11 17:25:28 |             MASTER- | (15h 26m 30.18s , +62d 47m 59.6s) |   C |    60 | 19.4 |        
   23221 | 2021-05-11 17:25:28 |             MASTER- | (15h 09m 29.85s , +61d 34m 46.4s) |   C |    60 | 18.7 |        
   23300 | 2021-05-11 17:26:47 |             MASTER- | (14h 49m 19.52s , +72d 48m 09.4s) |   C |    60 | 19.1 |        
   23300 | 2021-05-11 17:26:47 |             MASTER- | (14h 23m 34.81s , +71d 34m 01.5s) |   C |    60 | 18.4 |        
   23491 | 2021-05-11 17:29:58 |             MASTER- | (18h 30m 21.01s , +66d 40m 51.8s) |   C |    60 | 19.5 |        
   23491 | 2021-05-11 17:29:58 |             MASTER- | (18h 10m 52.05s , +65d 27m 32.9s) |   C |    60 | 18.7 |        
   23765 | 2021-05-11 17:34:34 |             MASTER- | (17h 42m 46.76s , +60d 42m 58.9s) |   C |    55 | 19.1 |        
   23765 | 2021-05-11 17:34:34 |             MASTER- | (17h 26m 52.89s , +59d 29m 53.8s) |   C |    55 | 18.1 |        
   23834 | 2021-05-11 17:35:43 |             MASTER- | (16h 00m 46.24s , +62d 48m 52.2s) |   C |    55 | 19.5 |        
   23834 | 2021-05-11 17:35:43 |             MASTER- | (15h 43m 47.03s , +61d 35m 29.0s) |   C |    55 | 18.3 |        
   24156 | 2021-05-11 17:41:03 |             MASTER- | (16h 38m 22.43s , +60d 47m 09.9s) |   C |    60 | 19.5 |        
   24156 | 2021-05-11 17:41:03 |             MASTER- | (16h 22m 26.61s , +59d 34m 01.1s) |   C |    60 | 18.4 |        
   24230 | 2021-05-11 17:42:17 |             MASTER- | (17h 46m 20.32s , +64d 42m 11.2s) |   C |    60 | 19.7 |        
   24230 | 2021-05-11 17:42:17 |             MASTER- | (17h 28m 12.03s , +63d 29m 11.9s) |   C |    60 | 18.4 |        
   24301 | 2021-05-11 17:43:28 |             MASTER- | (17h 10m 38.70s , +60d 45m 48.3s) |   C |    60 | 19.4 |        
   24301 | 2021-05-11 17:43:28 |             MASTER- | (16h 54m 42.78s , +59d 32m 46.4s) |   C |    60 | 18.1 |        
   24372 | 2021-05-11 17:44:39 |             MASTER- | (17h 43m 44.71s , +62d 43m 08.9s) |   C |    60 | 19.7 |        
   24372 | 2021-05-11 17:44:39 |             MASTER- | (17h 26m 48.02s , +61d 30m 11.3s) |   C |    60 | 18.0 |        
   24452 | 2021-05-11 17:45:59 |             MASTER- | (15h 11m 40.07s , +66d 50m 30.5s) |   C |    60 | 19.3 |        
   24452 | 2021-05-11 17:45:59 |             MASTER- | (14h 52m 04.52s , +65d 36m 37.0s) |   C |    60 | 18.7 |        
   24797 | 2021-05-11 17:51:44 |             MASTER- | (15h 18m 48.09s , +64d 49m 49.2s) |   C |    60 | 19.6 |        
   24797 | 2021-05-11 17:51:44 |             MASTER- | (15h 00m 41.28s , +63d 36m 13.8s) |   C |    60 | 18.4 |        
   24870 | 2021-05-11 17:52:57 |             MASTER- | (16h 06m 19.84s , +62d 55m 19.1s) |   C |    60 | 15.8 |        
   24870 | 2021-05-11 17:52:57 |             MASTER- | (15h 49m 20.71s , +61d 41m 43.4s) |   C |    60 | 15.8 |        
   24942 | 2021-05-11 17:54:08 |             MASTER- | (15h 26m 09.86s , +62d 48m 44.3s) |   C |    60 | 14.5 |        
   24942 | 2021-05-11 17:54:08 |             MASTER- | (15h 09m 15.13s , +61d 34m 56.6s) |   C |    60 | 13.7 |        
   25045 | 2021-05-11 17:55:52 |             MASTER- | (14h 31m 23.14s , +71d 45m 54.9s) |   C |    60 | 19.1 |        
   25045 | 2021-05-11 17:55:52 |             MASTER- | (14h 57m 17.21s , +72d 55m 43.0s) |   C |    60 | 18.4 |        
   25213 | 2021-05-11 17:58:40 |             MASTER- | (18h 30m 15.46s , +66d 39m 21.0s) |   C |    60 | 19.5 |        
   25213 | 2021-05-11 17:58:40 |             MASTER- | (18h 10m 43.88s , +65d 27m 45.9s) |   C |    60 | 18.4 |        
   25478 | 2021-05-11 18:03:05 |             MASTER- | (17h 42m 42.83s , +60d 43m 04.8s) |   C |    60 | 19.3 |        
   25478 | 2021-05-11 18:03:05 |             MASTER- | (17h 26m 46.73s , +59d 31m 10.4s) |   C |    60 | 18.0 |        
   25553 | 2021-05-11 18:04:20 |             MASTER- | (15h 43m 36.14s , +61d 33m 44.7s) |   C |    60 | 18.4 |        
   25553 | 2021-05-11 18:04:20 |             MASTER- | (16h 00m 38.15s , +62d 46m 07.8s) |   C |    60 | 19.6 |        
   25887 | 2021-05-11 18:09:54 |             MASTER- | (16h 38m 17.18s , +60d 46m 16.7s) |   C |    60 | 19.4 |        
   25887 | 2021-05-11 18:09:54 |             MASTER- | (16h 22m 19.22s , +59d 33m 33.8s) |   C |    60 | 18.4 |        
   25960 | 2021-05-11 18:11:06 |             MASTER- | (17h 27m 57.57s , +63d 29m 51.2s) |   C |    60 | 18.5 |        
   32102 | 2021-05-11 19:53:29 |   MASTER-Kislovodsk | (16h 21m 31.86s , +70d 10m 07.5s) |   C |    60 | 17.0 |        
   32102 | 2021-05-11 19:53:29 |   MASTER-Kislovodsk | (16h 33m 26.27s , +69d 44m 50.1s) |   C |    60 | 17.6 |        
   32463 | 2021-05-11 19:59:30 |   MASTER-Kislovodsk | (17h 04m 09.89s , +68d 09m 02.8s) |   C |    60 | 15.4 |        
   32463 | 2021-05-11 19:59:30 |   MASTER-Kislovodsk | (17h 15m 08.79s , +67d 43m 50.4s) |   C |    60 | 15.7 |        
   32543 | 2021-05-11 20:00:50 |   MASTER-Kislovodsk | (17h 08m 13.52s , +70d 10m 00.1s) |   C |    60 | 15.2 |        
   32543 | 2021-05-11 20:00:50 |   MASTER-Kislovodsk | (17h 20m 13.61s , +69d 44m 35.3s) |   C |    60 | 15.6 |        
   32623 | 2021-05-11 20:02:10 |   MASTER-Kislovodsk | (16h 22m 45.12s , +72d 09m 29.5s) |   C |    60 | 15.1 |        
   32624 | 2021-05-11 20:02:10 |   MASTER-Kislovodsk | (16h 36m 01.97s , +71d 44m 22.3s) |   C |    60 | 15.6 |        
   32704 | 2021-05-11 20:03:31 |   MASTER-Kislovodsk | (16h 21m 18.77s , +68d 08m 39.2s) |   C |    60 | 15.2 |        
   32704 | 2021-05-11 20:03:31 |   MASTER-Kislovodsk | (16h 32m 21.88s , +67d 43m 39.9s) |   C |    60 | 15.3 |        
   32864 | 2021-05-11 20:06:11 |   MASTER-Kislovodsk | (17h 01m 54.30s , +66d 10m 05.5s) |   C |    60 | 14.7 |        
   32864 | 2021-05-11 20:06:11 |   MASTER-Kislovodsk | (17h 12m 06.04s , +65d 45m 04.2s) |   C |    60 | 15.2 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210511B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29996
SUBJECT: GRB 210511B: Fermi GBM observation
DATE:    21/05/11 21:37:39 GMT
FROM:    Elisabetta Bissaldi at INFN,Bari  <elisabetta.bissaldi@ba.infn.it>

E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:


"At 11:26:39.26 UT on 11 May 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210511B (trigger 642425204 / 210511477),
which was also detected by GECAM (Cai et al., GCN 29990) and
by AGILE (Ursi et al., GCN 29991).
The Fermi GBM Final Real-time Localization was reported in GCN 29988.

The angle from the Fermi LAT boresight at the GBM trigger time is 49 degrees.

The GBM light curve consists of a bright emission episode
with a duration (T90) of about 6 s (50-300 keV).
The time-averaged spectrum from T0 to T0+8 s is
best fit by a Band function with Epeak = 128 +/- 5 keV,
alpha = -0.72 +/- 0.04, and beta = -2.47 +/- 0.10.

The event fluence (10-1000 keV) in this time interval is
(1.04 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.2 s in the 10-1000 keV band
is 23.3 +/- 0.3 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210427A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29997
SUBJECT: IPN triangulation of GRB 210427A
DATE:    21/05/11 22:57:01 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration GRB 210427A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29903;
BALROG localization: Biltzinger et al., GCN Circ. 29905;
GECAM detection: Xie et al., GCN Circ. 29906)
was detected by Fermi (GBM trigger 641192237), Konus-Wind,
Swift (BAT), outside the coded FoV, Mars-Odyssey (HEND),
and GECAM-B at about 17832 s UT (04:57:12).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   177.792 (11h 51m 10s) -52.866 (-52d 51' 57")
  Corners:
   176.862 (11h 47m 27s) -54.591 (-54d 35' 28")
   176.750 (11h 47m 00s) -54.533 (-54d 31' 59")
   178.678 (11h 54m 43s) -51.138 (-51d 08' 18")
   178.782 (11h 55m 08s) -51.196 (-51d 11' 46")
  ---------------------------------------------
The error box area is 1036 sq. arcmin, and its maximum
dimension is 3.6 deg (the minimum one is 4.8 arcmin).
The Sun distance was 93 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations (GCN Circ. 29903 and 29905).
It was inside the Transiting Exoplanet Survey Satellite (TESS)
field of view.

We thank Robert Wilson for pointing out the TESS/IPN coincidence.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210427_T17835/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210511B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29998
SUBJECT: GRB 210511B: DDOTI Upper Limits on the Afterglow
DATE:    21/05/12 00:14:52 GMT
FROM:    Kin O. C. L. Mendoza at Instituto de Astronoma, UNAM  <koclopez@astro.unam.mx>

OcÃ©lotl Lopez (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L.
Becerra (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD),
William H. Lee (UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM),
Srihari Ravi (ASU), and
Eleonora Troja (GSFC/UMD) report:

We observed the field of the Fermi - GBM event GRB 210511B (Fermi
Collaboration, GCN Circ. 29988) with the DDOTI wide-field imager at the
Observatorio AstronÃ³mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-05-11 11:49:26 to 12:01:38 UTC
(0.38 to 0.58 hours after the trigger) and obtained 6 minutes of exposure
in the w filter. The images were obtained after the astronomical twilight.

We observed a region covering approximately 14 degrees in RA and 10 degrees
in declination, with a 2 x 1 grid, including the entire initial uncertainty
region distributed in the GCN Notice (Fermi Collaboration, GCN Circ. 29988)

Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point
sources to a 10-sigma limiting magnitude of w = 18.39.

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
Martir.


GRB_name: GRB210323A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30000
SUBJECT: Short GRB 210323A: likely host galaxy detection
DATE:    21/05/12 14:38:46 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>

Daniele B. Malesani (DTU Space), Luca Izzo (DARK/NBI) and Andrea Rossi 
(INAF/OAS) report on behalf of a larger collaboration.

We observed again the field of the short GRB 210323A (Gropp et al., GCN 
29699). We used the ALFOSC camera at the Nordic Optical Telescope (NOT). 
Observations were carried out during the night of 2021 May 4, 
approximately 42.3 days after the GRB, and consisted of 5x600 s exposure 
in the r band.

The optical source detected in our earlier observation (Malesani et al., 
GCN 29703; see also Pozanenko et al., GCN 29708; de Ugarte Postigo et 
al., GCN 29717; Rastinejad et al., GCN 29720) has clearly faded, 
confirming it is the afterglow of GRB 210323A. Directly underneath the 
position of the optical transient, a faint source is visible in the 
stack of our images, which is likely the host galaxy of the GRB (see 
also Rastinejad et al., GCN 29720).

We measure for the host an AB magnitude r = 24.6 +- 0.3, calibrated 
against nearby stars from the Pan-STARRS catalogue.

We acknowledge expert help from the support astronomer at the NOT, 
Amanda Djupvik.


GRB_name: GRB210511B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30002
SUBJECT: IPN triangulation of GRB 210511B
DATE:    21/05/12 18:15:02 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration GRB 210511B
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29988;
Bissaldi and Meegan, GCN Circ. 29996;
BALROG localization: Kunzweiler et al., GCN Circ. 29989;
GECAM detection: Cai et al., GCN Circ. 29990;
AGILE detection: Ursi et al., GCN Circ. 29991)
was detected by Fermi (GBM trigger 642425204), Konus-Wind,
Mars-Odyssey (HEND), INTEGRAL (SPI-ACS), AGILE and GECAM-B
at about 41199 s UT (11:26:39).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   312.914 (20h 51m 39s) +58.375 (+58d 22' 31")
  Corners:
   306.385 (20h 25m 33s) +59.894 (+59d 53' 39")
   306.250 (20h 25m 00s) +60.029 (+60d 01' 45")
   318.903 (21h 15m 37s) +56.519 (+56d 31' 10")
   318.984 (21h 15m 56s) +56.371 (+56d 22' 16")
  ---------------------------------------------
The error box area is 2687 sq. arcmin, and its maximum
dimension is 7.6 deg (the minimum one is 6.0 arcmin).
The Sun distance was 75 deg.

This box may be improved.

This error box is consistent with, but reduces the areas of, the Fermi 
(RoboBA and BALROG), and GECAM localizations.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210511_T41201/IPN

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210510A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30005
SUBJECT: GRB210510A: Optical afterglow candidate from the Zwicky Transient Facility
DATE:    21/05/13 03:13:19 GMT
FROM:    Shreya Anand at GROWTH Caltech  <sanand@caltech.edu>

Shreya Anand (Caltech), Igor Andreoni (Caltech), Tomas Ahumada (UMD), Erik Kool (SU), Ana Sagues-Carracedo (SU), Simeon Reusch (DESY), Mansi Kasliwal (Caltech), Michael Coughlin (UMN), Harsh Kumar (IIT-B), Robert Stein (DESY), Leo Singer (NASA/GSFC), Matthew Graham (Caltech) on behalf of the ZTF collaboration

We observed the localization region of the short GRB210510A (trigger 642367205) detected by the Gamma-Ray Burst Monitor (GBM) on the Fermi satellite with the Palomar 48 inch telescope equipped with the 47 square degree Zwicky Transient Facility (ZTF; Bellm et al., 2019; Graham et al., 2019) camera. We obtained a series of g- and r-band images covering about 1105 square degrees beginning at 05:02:53.10 UT on 2021-05-11 (~ 10 hours after the burst trigger time). This corresponds to ~84% of the probability enclosed in the region of the GRB localization map that was unocculted by the Earth for the Fermi GBM (GCN 28965). Exposures reached a median depth of 22.1 mag in the g-band and 22.0 mag in the r-band. On 2021-05-12, we obtained another epoch of r-band follow-up observations, beginning at 05:01:58.00 UT with exposures reaching a median depth of 22.1 mag and and covering ~81% of the enclosed probability.

The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019). We queried the ZTF alert stream using Kowalski (Duev et al. 2019). We required at least 2 detections separated by at least 15 minutes to select against moving objects. Furthermore, we cross-matched our candidates with the Minor Planet Center to flag known asteroids, reject stellar sources (Tachibana and Miller 2018), and apply machine learning algorithms (Duev et al. 2019, Mahabal et al. 2019). We require no spatially coincident ZTF alert to be issued before the detection time of the GBM trigger. 

We identified 186 transient candidates located within the 95% probability contour of the skymap that passed automatic selection criteria and human vetting from two nights of follow-up. Amongst these candidates, only one candidate (ZTF21abaytuk, shown below) passes these criteria and evolves faster than 0.3 mag/day.

+--------------+-----------+-------------+--------------+--------+-------+-----------+
|   Name   | IAU Name |   RA   |   Dec   | filter | mag  |  MJD   |
+--------------+-----------+-------------+--------------+--------+-------+-----------+
| ZTF21abaytuk | AT2021meo | 13:48:49.89 | +35:32:13.05 |  g  | 21.76 | 59345.224 |
+--------------+-----------+-------------+--------------+--------+-------+-----------+

ZTF21abaytuk has a decay rate of 0.36 mag/day in the r-band from ZTF IPAC Forced photometry (Masci et al. 2018), and a color of g-r~0.5 mag, consistent with the expected red colors of an afterglow. This transient was discovered in a galaxy host with an SDSS photometric redshift of 0.221  0.0742, whose WISE colors indicate that it may be an AGN. ZTF21abaytuk was found to be significantly variable by the ZTF Realtime Search and Triggering (ZTFReST) pipeline (Andreoni & Coughlin et al. 2021). We encourage further photometric and spectroscopic observations.

Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Grant No. AST-2034437 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, Deutsches Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and UW.


GRB_name: GRB210511B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30007
SUBJECT: Konus-Wind detection of GRB 210511B
DATE:    21/05/13 20:48:20 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long-duration GRB 210511B
(Fermi GBM detection: Fermi GBM team, GCN 29988;
Bissaldi and Meegan, GCN 29996;
BALROG localization: Kunzweiler et al., GCN 29989;
GECAM detection: Cai et al., GCN 29990;
AGILE detection: Ursi et al., GCN 29991;
IPN triangulation: Hurley et al., GCN 30002)
triggered Konus-Wind at T0=41201.35 s UT (11:26:41.350).

The burst light curve shows a multi-peaked structure
which starts at ~T0-1.7 s and has a total duration of ~6 s.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210511_T41201/

As observed by Konus-Wind, the burst
had a fluence of 1.10(-0.15,+0.18)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.512 s,
of 4.76(-1.24,+1.34)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 4 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.98(-0.15,+0.18),
the high energy photon index beta = -2.48(-0.43,+0.23),
the peak energy Ep = 154(-22,+25) keV
(chi2 = 86/71 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB210514A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30008
SUBJECT: GRB 210514A: Swift detection of a burst
DATE:    21/05/14 19:02:01 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA), N. J. Klingler (PSU),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
B. Sbarufatti (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

The Swift Burst Alert Telescope (BAT) has triggered on a new event and Swift has
slewed to the location of this trigger. The trigger time is believed to be no
earlier than 17:08 UT. Given the loss of real-time antennae for half the sky, we
are unable to confirm the nature, location, or exact time of this trigger until
the full data have been downloaded, in approximately 3 hours (by around 22:00 UT). 

Limited XRT and UVOT data have been received. No counterpart is detected; however,
given the location of the image centre, we infer that the BAT position must have
been around RA,Dec = 2.9670, -21.8750 degrees (J2000), with an uncertainty of 12â€™. 

Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210514A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30009
SUBJECT: GRB 210514A: update on the BAT trigger time and burst duration
DATE:    21/05/15 00:05:01 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

A. Y. Lien (GSFC/UMBC) and E. Ambrosi (INAF-IASFPA)
report on behalf of the Neil Gehrels Swift Observatory Team:

We received further data from the recent telemetry downlink.
The trigger time for GRB 210514A (Swift trigger #1048372;
Ambrosi et al., GCN Circ. 30008) is
2021-05-14T18:23:47 UTC.

Based on currently available data from T-61 to T+242 sec,
the BAT ground-calculated position is
RA, Dec = 2.945, -21.898 deg which is
   RA(J2000)  =  00h 11m 46.8s
   Dec(J2000) = -21d 53' 52.1"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.

The BAT mask-weighted light curve shows a multi-peaked structure
with a total duration of ~80 s.

Using 1.3 ks of the XRT data in Window Timing mode,
the XRT location is RA,Dec = 2.95362, -21.88562 deg.


GRB_name: GRB210514A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30011
SUBJECT: GRB 210514A: Enhanced Swift-XRT position
DATE:    21/05/15 08:19:53 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 3253 s of XRT Photon Counting mode data and 8 UVOT
images for GRB 210514A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 2.96184, -21.89454 which is equivalent
to:

RA (J2000): 00h 11m 50.84s
Dec (J2000): -21d 53' 40.3"

with an uncertainty of 2.0 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210514A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30012
SUBJECT: GRB 210514A: Swift-XRT refined Analysis
DATE:    21/05/15 08:29:00 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), M.G. Bernardini (INAF-OAB), M. Capalbi (INAF-IASFPA), A.
Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU) and E.
Ambrosi report on behalf of the Swift-XRT team:

We have analysed 6.7 ks of XRT data for GRB 210514A (Ambrosi et al. GCN
Circ. 30008), from 60 s to 23.8 ks after the  BAT trigger. The data
comprise 1.4 ks in Windowed Timing (WT) mode (the first 8 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 30011). We cannot determine at the present time whether
the source is fading.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.06 (+/-0.04). The
best-fitting absorption column is  4.79 (+/-0.22) x 10^21 cm^-2, in
excess of the Galactic value of 2.0 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.95 (+0.12, -0.11)
and a best-fitting absorption column of 4.7 (+0.7, -0.6) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.1 x 10^-11 (6.5 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.7 (+0.7, -0.6) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: 12.2 sigma
Photon index:      1.95 (+0.12, -0.11)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01048372.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210514A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30013
SUBJECT: GRB 210514A: Swift XRT light curve is fading
DATE:    21/05/15 08:45:43 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

GCN Circular 30012 stated that we cannot determine whether the XRT afterglow of GRB 210514A is fading. This was incorrect. The light curve shows the so-called â€˜canonicalâ€™ X-ray afterglow behaviour, and can be modelled thus:

Alpha_1 : 3.44  (+0.14,  -0.15)
Tbreak_1: 141   (+6,     -5)    sec 
Alpha_2 : 1.22  (+0.18,  -0.17)
Tbreak_2: 276.7 (+16.8,  -15.6) sec
Alpha_3 : -0.14 (+0.06,  -0.05)
Tbreak_3: (1.02 [+0.04,  -0.03]) Ã— 10^3 sec
Alpha_4 : 1.236 (+0.024, -0.022)


We apologise for the confusion; this was the result of the automated XRT software not operating completely correctly in the circumstances that some of the prompt TDRSS messages are missing. We are working urgently to understand and rectify these issues.

The online analysis is available at the usual website (https://www.swift.ac.uk/xrt_products/01048372).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210515A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30015
SUBJECT: GRB 210515A: Fermi GBM Final Real-time Localization
DATE:    21/05/15 13:17:09 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 13:06:45 UT on 15 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210515A (trigger 642776810.702128 / 210515546).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 117.1, Dec = 77.3 (J2000 degrees, equivalent to J2000 07h 48m, 77d 17'), with a statistical uncertainty of 14.6 degrees.

The angle from the Fermi LAT boresight is 24.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210515546/quicklook/glg_skymap_all_bn210515546.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210515546/quicklook/glg_healpix_all_bn210515546.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210515546/quicklook/glg_lc_medres34_bn210515546.gif


GRB_name: GRB210515B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30016
SUBJECT: GRB 210515B: Fermi GBM Final Real-time Localization
DATE:    21/05/15 15:07:00 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 14:56:46 UT on 15 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210515B (trigger 642783411.180128 / 210515623).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 315.2, Dec = 45.7 (J2000 degrees, equivalent to J2000 21h 00m, 45d 42'), with a statistical uncertainty of 1.6 degrees.

The angle from the Fermi LAT boresight is 151.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210515623/quicklook/glg_skymap_all_bn210515623.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210515623/quicklook/glg_healpix_all_bn210515623.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210515623/quicklook/glg_lc_medres34_bn210515623.gif


GRB_name: GRB210515A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30017
SUBJECT: Fermi GRB 210515A: Global MASTER-Net observations report 
DATE:    21/05/15 17:30:42 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210515A ( Fermi GBM team, GCN 30015) errorbox  15309 sec after notice time and 15341 sec after trigger time at 2021-05-15 17:22:27 UT, with upper limit up to  17.3 mag. Observations started at twilight.  The observations began at zenith distance = 37 deg. The sun  altitude  is -9.4 deg. 

The galactic latitude b = 30 deg., longitude l = 137 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1613638

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    3360 | 2021-05-15 14:02:44 |             MASTER- | (07h 25m 13.45s , +74d 51m 35.7s) |   C |     1 | 13.3 |        
    3385 | 2021-05-15 14:03:09 |             MASTER- | (08h 25m 22.23s , +73d 00m 58.9s) |   C |     1 | 15.4 |        
    3397 | 2021-05-15 14:03:21 |             MASTER- | (08h 53m 49.61s , +73d 03m 11.9s) |   C |     1 | 15.6 |        
    3409 | 2021-05-15 14:03:33 |             MASTER- | (09h 19m 15.99s , +73d 04m 50.7s) |   C |     1 | 15.2 |        
    3569 | 2021-05-15 14:06:13 |             MASTER- | (10h 02m 05.40s , +75d 00m 33.9s) |   C |     1 | 15.5 |        
    3586 | 2021-05-15 14:06:30 |             MASTER- | (09h 11m 17.12s , +71d 10m 05.6s) |   C |     1 | 15.2 |        
    3597 | 2021-05-15 14:06:41 |             MASTER- | (09h 36m 50.52s , +71d 13m 01.5s) |   C |     1 | 15.5 |        
    3610 | 2021-05-15 14:06:54 |             MASTER- | (08h 53m 09.40s , +76d 50m 50.5s) |   C |     1 | 15.0 |        
    3630 | 2021-05-15 14:07:15 |             MASTER- | (09h 44m 41.08s , +76d 54m 28.7s) |   C |     1 | 15.6 |        
    3642 | 2021-05-15 14:07:27 |             MASTER- | (10h 21m 25.83s , +76d 56m 13.2s) |   C |     1 | 15.7 |        
    3659 | 2021-05-15 14:07:43 |             MASTER- | (08h 22m 50.86s , +71d 09m 01.8s) |   C |     1 | 15.6 |        
    3674 | 2021-05-15 14:07:58 |             MASTER- | (08h 48m 18.89s , +71d 09m 15.3s) |   C |     1 | 16.0 |        
    3688 | 2021-05-15 14:08:13 |             MASTER- | (07h 31m 40.82s , +72d 58m 08.0s) |   C |     1 | 15.4 |        
    3705 | 2021-05-15 14:08:29 |             MASTER- | (07h 59m 50.87s , +73d 01m 15.7s) |   C |     1 | 15.5 |        
    3731 | 2021-05-15 14:08:55 |             MASTER- | (08h 21m 13.75s , +69d 12m 47.4s) |   C |     1 | 15.5 |        
    3745 | 2021-05-15 14:09:09 |             MASTER- | (08h 44m 26.50s , +69d 14m 52.3s) |   C |     1 | 15.3 |        
    3758 | 2021-05-15 14:09:22 |             MASTER- | (08h 43m 05.71s , +78d 43m 51.9s) |   C |     1 | 14.7 |        
    3771 | 2021-05-15 14:09:35 |             MASTER- | (09h 26m 14.42s , +78d 49m 01.9s) |   C |     1 | 15.7 |        
    4098 | 2021-05-15 14:15:00 |             MASTER- | (09h 28m 27.33s , +69d 18m 06.0s) |   C |     5 | 16.6 |        
    4118 | 2021-05-15 14:15:21 |             MASTER- | (10h 05m 08.97s , +78d 49m 34.8s) |   C |     5 | 16.5 |        
    4135 | 2021-05-15 14:15:37 |             MASTER- | (10h 48m 22.93s , +78d 53m 18.1s) |   C |     5 | 16.5 |        
    4156 | 2021-05-15 14:15:59 |             MASTER- | (09h 00m 54.68s , +67d 23m 36.1s) |   C |     5 | 16.6 |        
    4171 | 2021-05-15 14:16:15 |             MASTER- | (09h 22m 05.07s , +67d 23m 53.4s) |   C |     1 | 15.8 |        
    4187 | 2021-05-15 14:16:32 |             MASTER- | (10h 30m 49.59s , +75d 03m 17.5s) |   C |     1 | 16.4 |        
    4199 | 2021-05-15 14:16:44 |             MASTER- | (11h 02m 52.01s , +75d 03m 43.1s) |   C |     1 | 16.0 |        
    4220 | 2021-05-15 14:17:04 |             MASTER- | (07h 47m 17.95s , +71d 04m 17.5s) |   C |     1 | 15.7 |        
    4240 | 2021-05-15 14:17:24 |             MASTER- | (08h 20m 27.31s , +67d 18m 39.5s) |   C |     1 | 15.6 |        
    4253 | 2021-05-15 14:17:38 |             MASTER- | (08h 41m 44.08s , +67d 21m 56.7s) |   C |     1 | 15.8 |        
    4266 | 2021-05-15 14:17:50 |             MASTER- | (08h 44m 59.01s , +74d 57m 01.4s) |   C |     1 | 15.7 |        
    4278 | 2021-05-15 14:18:02 |             MASTER- | (08h 55m 38.49s , +80d 40m 01.9s) |   C |     1 | 15.7 |        
    4291 | 2021-05-15 14:18:15 |             MASTER- | (09h 47m 58.34s , +80d 42m 22.7s) |   C |     1 | 15.7 |        
    4306 | 2021-05-15 14:18:30 |             MASTER- | (08h 25m 24.08s , +73d 01m 41.5s) |   C |     1 | 15.8 |        
    4318 | 2021-05-15 14:18:42 |             MASTER- | (08h 53m 36.11s , +73d 04m 50.5s) |   C |     1 | 15.9 |        
    4331 | 2021-05-15 14:18:55 |             MASTER- | (09h 19m 08.83s , +73d 04m 49.0s) |   C |     1 | 15.6 |        
    4353 | 2021-05-15 14:19:18 |             MASTER- | (07h 28m 38.49s , +74d 51m 37.9s) |   C |     1 | 16.1 |        
    4366 | 2021-05-15 14:19:30 |             MASTER- | (08h 00m 21.14s , +74d 55m 05.2s) |   C |     1 | 16.5 |        
    4381 | 2021-05-15 14:19:46 |             MASTER- | (09h 47m 30.86s , +73d 07m 07.7s) |   C |     1 | 15.9 |        
    4394 | 2021-05-15 14:19:58 |             MASTER- | (09h 41m 18.83s , +67d 24m 01.2s) |   C |     1 | 16.1 |        
    4406 | 2021-05-15 14:20:10 |             MASTER- | (10h 02m 31.74s , +67d 26m 34.1s) |   C |     1 | 15.9 |        
    4427 | 2021-05-15 14:20:31 |             MASTER- | (07h 40m 14.23s , +67d 16m 42.9s) |   C |     1 | 15.8 |        
    4439 | 2021-05-15 14:20:43 |             MASTER- | (08h 01m 18.98s , +67d 17m 47.8s) |   C |     1 | 16.1 |        
    4481 | 2021-05-15 14:21:25 |             MASTER- | (09h 29m 47.94s , +74d 59m 39.8s) |   C |     1 | 16.0 |        
    4493 | 2021-05-15 14:21:38 |             MASTER- | (10h 01m 45.91s , +75d 00m 41.7s) |   C |     1 | 16.1 |        
    4507 | 2021-05-15 14:21:51 |             MASTER- | (09h 11m 11.06s , +71d 10m 00.8s) |   C |     1 | 16.1 |        
    4521 | 2021-05-15 14:22:05 |             MASTER- | (09h 36m 37.56s , +71d 12m 58.4s) |   C |     1 | 16.2 |        
    4539 | 2021-05-15 14:22:21 |             MASTER- | (08h 53m 00.69s , +76d 50m 43.9s) |   C |     5 | 17.0 |        
    4556 | 2021-05-15 14:22:39 |             MASTER- | (09h 44m 24.66s , +76d 55m 36.8s) |   C |     5 | 16.9 |        
    4577 | 2021-05-15 14:22:59 |             MASTER- | (10h 21m 08.70s , +76d 56m 49.3s) |   C |     5 | 17.1 |        
    4597 | 2021-05-15 14:23:19 |             MASTER- | (08h 22m 41.72s , +71d 08m 36.5s) |   C |     5 | 16.9 |        
    4613 | 2021-05-15 14:23:35 |             MASTER- | (08h 48m 14.59s , +71d 09m 21.6s) |   C |     5 | 17.0 |        
    4635 | 2021-05-15 14:23:57 |             MASTER- | (07h 31m 38.23s , +72d 56m 28.2s) |   C |     5 | 17.0 |        
    4651 | 2021-05-15 14:24:13 |             MASTER- | (07h 59m 53.34s , +72d 58m 50.1s) |   C |     5 | 16.9 |        
    4667 | 2021-05-15 14:24:29 |             MASTER- | (08h 21m 10.92s , +69d 13m 55.4s) |   C |     5 | 16.8 |        
    4684 | 2021-05-15 14:24:46 |             MASTER- | (08h 44m 19.48s , +69d 14m 17.5s) |   C |     5 | 17.0 |        
    4704 | 2021-05-15 14:25:06 |             MASTER- | (08h 42m 55.10s , +78d 45m 41.2s) |   C |     5 | 17.1 |        
    4721 | 2021-05-15 14:25:23 |             MASTER- | (09h 25m 55.62s , +78d 47m 38.4s) |   C |     5 | 17.4 |        
    4737 | 2021-05-15 14:25:39 |             MASTER- | (09h 59m 30.31s , +71d 14m 29.7s) |   C |     5 | 17.0 |        
    4759 | 2021-05-15 14:26:02 |             MASTER- | (07h 21m 33.21s , +78d 37m 36.9s) |   C |     5 | 17.2 |        
    4776 | 2021-05-15 14:26:18 |             MASTER- | (08h 04m 21.34s , +78d 41m 01.1s) |   C |     5 | 17.0 |        
    4792 | 2021-05-15 14:26:35 |             MASTER- | (07h 42m 37.21s , +80d 35m 07.6s) |   C |     5 | 17.2 |        
    4819 | 2021-05-15 14:27:01 |             MASTER- | (10h 25m 06.35s , +71d 13m 57.7s) |   C |     5 | 17.4 |        
    4838 | 2021-05-15 14:27:20 |             MASTER- | (10h 13m 01.93s , +73d 08m 39.9s) |   C |     5 | 17.3 |        
    4864 | 2021-05-15 14:27:46 |             MASTER- | (06h 38m 16.65s , +72d 53m 32.4s) |   C |     5 | 16.9 |        
    4880 | 2021-05-15 14:28:02 |             MASTER- | (07h 06m 25.42s , +72d 54m 50.0s) |   C |     5 | 17.0 |        
    4913 | 2021-05-15 14:28:35 |             MASTER- | (09h 49m 14.88s , +69d 17m 47.0s) |   C |     5 | 16.7 |        
    4936 | 2021-05-15 14:28:59 |             MASTER- | (10h 12m 23.14s , +69d 20m 33.5s) |   C |     5 | 17.4 |        
    4962 | 2021-05-15 14:29:24 |             MASTER- | (07h 25m 23.12s , +76d 45m 04.1s) |   C |     5 | 17.1 |        
    4978 | 2021-05-15 14:29:41 |             MASTER- | (08h 01m 40.60s , +76d 47m 24.8s) |   C |     5 | 17.2 |        
    4996 | 2021-05-15 14:29:59 |             MASTER- | (09h 05m 04.59s , +69d 16m 52.9s) |   C |     5 | 17.3 |        
    5015 | 2021-05-15 14:30:17 |             MASTER- | (09h 28m 21.44s , +69d 17m 17.8s) |   C |     5 | 17.5 |        
    5032 | 2021-05-15 14:30:34 |             MASTER- | (10h 04m 48.30s , +78d 48m 42.6s) |   C |     5 | 17.6 |        
    5053 | 2021-05-15 14:30:56 |             MASTER- | (10h 48m 13.15s , +78d 50m 57.1s) |   C |     5 | 17.6 |        
    5074 | 2021-05-15 14:31:16 |             MASTER- | (09h 00m 46.42s , +67d 22m 35.9s) |   C |     5 | 17.2 |        
    5095 | 2021-05-15 14:31:35 |             MASTER- | (09h 22m 02.08s , +67d 22m 25.4s) |   C |    10 | 18.0 |        
    5122 | 2021-05-15 14:32:02 |             MASTER- | (10h 30m 36.53s , +75d 03m 43.3s) |   C |    10 | 18.1 |        
    5143 | 2021-05-15 14:32:23 |             MASTER- | (11h 02m 38.11s , +75d 04m 18.1s) |   C |    10 | 18.0 |        
    5173 | 2021-05-15 14:32:53 |             MASTER- | (07h 47m 07.28s , +71d 05m 13.6s) |   C |    10 | 17.6 |        
    5194 | 2021-05-15 14:33:14 |             MASTER- | (08h 20m 26.50s , +67d 18m 40.3s) |   C |    10 | 17.7 |        
    5216 | 2021-05-15 14:33:36 |             MASTER- | (08h 41m 34.61s , +67d 19m 08.6s) |   C |    10 | 17.6 |        
    5237 | 2021-05-15 14:33:57 |             MASTER- | (08h 44m 59.33s , +74d 55m 41.7s) |   C |    10 | 17.7 |        
    5259 | 2021-05-15 14:34:19 |             MASTER- | (08h 55m 18.56s , +80d 39m 46.0s) |   C |    10 | 18.0 |        
    5281 | 2021-05-15 14:34:41 |             MASTER- | (09h 47m 43.52s , +80d 42m 01.2s) |   C |    10 | 17.9 |        
    5308 | 2021-05-15 14:35:08 |             MASTER- | (08h 25m 15.15s , +73d 02m 11.3s) |   C |    10 | 17.2 |        
    5329 | 2021-05-15 14:35:29 |             MASTER- | (08h 53m 26.38s , +73d 03m 10.4s) |   C |    10 | 17.7 |        
    5349 | 2021-05-15 14:35:50 |             MASTER- | (09h 18m 54.51s , +73d 05m 49.2s) |   C |    10 | 17.7 |        
    5395 | 2021-05-15 14:36:35 |             MASTER- | (08h 00m 17.44s , +74d 52m 01.6s) |   C |    10 | 17.8 |        
    5420 | 2021-05-15 14:37:01 |             MASTER- | (09h 47m 21.68s , +73d 05m 24.8s) |   C |    10 | 18.0 |        
    5442 | 2021-05-15 14:37:22 |             MASTER- | (09h 41m 08.24s , +67d 24m 36.9s) |   C |    10 | 18.2 |        
    5464 | 2021-05-15 14:37:44 |             MASTER- | (10h 02m 25.59s , +67d 24m 18.2s) |   C |    10 | 18.4 |        
    5491 | 2021-05-15 14:38:11 |             MASTER- | (07h 40m 13.15s , +67d 15m 47.7s) |   C |    10 | 17.3 |        
    5513 | 2021-05-15 14:38:33 |             MASTER- | (08h 01m 16.03s , +67d 16m 43.0s) |   C |    10 | 17.6 |        
    5567 | 2021-05-15 14:39:27 |             MASTER- | (09h 29m 38.20s , +74d 58m 52.0s) |   C |    10 | 17.8 |        
    5588 | 2021-05-15 14:39:49 |             MASTER- | (10h 01m 32.90s , +74d 59m 54.0s) |   C |    10 | 17.9 |        
    5611 | 2021-05-15 14:40:12 |             MASTER- | (09h 11m 03.15s , +71d 09m 21.5s) |   C |    10 | 18.0 |        
    5635 | 2021-05-15 14:40:33 |             MASTER- | (09h 36m 28.39s , +71d 12m 06.1s) |   C |    15 | 18.6 |        
    5662 | 2021-05-15 14:40:59 |             MASTER- | (08h 52m 49.29s , +76d 49m 44.3s) |   C |    15 | 18.3 |        
    5690 | 2021-05-15 14:41:27 |             MASTER- | (09h 44m 09.66s , +76d 54m 44.1s) |   C |    15 | 18.1 |        
    5719 | 2021-05-15 14:41:56 |             MASTER- | (10h 20m 53.08s , +76d 56m 04.4s) |   C |    15 | 18.4 |        
    5751 | 2021-05-15 14:42:28 |             MASTER- | (08h 22m 35.79s , +71d 07m 33.9s) |   C |    15 | 18.1 |        
    5776 | 2021-05-15 14:42:53 |             MASTER- | (08h 48m 06.82s , +71d 08m 21.9s) |   C |    15 | 18.1 |        
    5804 | 2021-05-15 14:43:22 |             MASTER- | (07h 31m 35.47s , +72d 55m 20.2s) |   C |    15 | 17.8 |        
    5831 | 2021-05-15 14:43:48 |             MASTER- | (07h 59m 47.58s , +72d 57m 56.7s) |   C |    15 | 18.1 |        
    5856 | 2021-05-15 14:44:14 |             MASTER- | (08h 21m 05.82s , +69d 12m 58.4s) |   C |    15 | 17.5 |        
    5882 | 2021-05-15 14:44:39 |             MASTER- | (08h 44m 12.69s , +69d 13m 12.7s) |   C |    15 | 18.1 |        
    5911 | 2021-05-15 14:45:08 |             MASTER- | (08h 42m 41.57s , +78d 44m 20.3s) |   C |    15 | 18.4 |        
    5938 | 2021-05-15 14:45:36 |             MASTER- | (09h 25m 38.84s , +78d 46m 39.6s) |   C |    15 | 18.6 |        
    5965 | 2021-05-15 14:46:02 |             MASTER- | (09h 59m 21.13s , +71d 13m 37.8s) |   C |    15 | 18.5 |        
    5998 | 2021-05-15 14:46:33 |             MASTER- | (07h 21m 31.57s , +78d 37m 23.4s) |   C |    20 | 18.4 |        
    6031 | 2021-05-15 14:47:06 |             MASTER- | (08h 04m 05.10s , +78d 39m 45.8s) |   C |    20 | 18.4 |        
    6062 | 2021-05-15 14:47:37 |             MASTER- | (07h 42m 35.78s , +80d 32m 25.1s) |   C |    20 | 18.4 |        
    6099 | 2021-05-15 14:48:14 |             MASTER- | (10h 24m 54.16s , +71d 14m 23.1s) |   C |    20 | 18.1 |        
    6129 | 2021-05-15 14:48:44 |             MASTER- | (10h 12m 46.11s , +73d 06m 24.8s) |   C |    20 | 18.5 |        
    6169 | 2021-05-15 14:49:24 |             MASTER- | (06h 38m 27.25s , +72d 52m 02.8s) |   C |    20 | 17.9 |        
    6200 | 2021-05-15 14:49:55 |             MASTER- | (07h 06m 19.36s , +72d 53m 30.4s) |   C |    20 | 18.1 |        
    6240 | 2021-05-15 14:50:35 |             MASTER- | (10h 41m 06.48s , +73d 09m 30.4s) |   C |    20 | 13.8 |        
    6272 | 2021-05-15 14:51:08 |             MASTER- | (09h 49m 05.98s , +69d 17m 49.1s) |   C |    20 | 18.6 |        
    6379 | 2021-05-15 14:52:54 |             MASTER- | (07h 25m 20.76s , +76d 42m 23.2s) |   C |    20 | 18.1 |        
    6410 | 2021-05-15 14:53:26 |             MASTER- | (08h 01m 34.45s , +76d 47m 05.4s) |   C |    20 | 18.2 |        
    6443 | 2021-05-15 14:53:58 |             MASTER- | (09h 04m 59.70s , +69d 14m 03.4s) |   C |    20 | 18.6 |        
    6473 | 2021-05-15 14:54:28 |             MASTER- | (09h 28m 11.12s , +69d 16m 57.0s) |   C |    20 | 18.7 |        
    6505 | 2021-05-15 14:55:00 |             MASTER- | (10h 04m 23.80s , +78d 48m 34.9s) |   C |    20 | 18.8 |        
    6537 | 2021-05-15 14:55:32 |             MASTER- | (10h 47m 39.49s , +78d 51m 59.4s) |   C |    20 | 18.8 |        
    6997 | 2021-05-15 15:03:12 |             MASTER- | (11h 02m 22.67s , +75d 04m 58.0s) |   C |    20 | 18.9 |        
    7036 | 2021-05-15 15:03:51 |             MASTER- | (07h 47m 06.87s , +71d 02m 49.0s) |   C |    20 | 18.7 |        
    7068 | 2021-05-15 15:04:24 |             MASTER- | (08h 20m 17.88s , +67d 18m 18.3s) |   C |    20 | 18.3 |        
    7098 | 2021-05-15 15:04:53 |             MASTER- | (08h 41m 35.56s , +67d 18m 49.3s) |   C |    20 | 18.6 |        
    7132 | 2021-05-15 15:05:27 |             MASTER- | (08h 54m 59.95s , +80d 36m 45.5s) |   C |    20 | 18.9 |        
    7463 | 2021-05-15 15:10:59 |             MASTER- | (07h 28m 34.50s , +74d 49m 55.5s) |   C |    20 | 18.6 |        
    7494 | 2021-05-15 15:11:29 |             MASTER- | (08h 00m 19.69s , +74d 51m 23.9s) |   C |    20 | 18.7 |        
    7530 | 2021-05-15 15:12:05 |             MASTER- | (09h 40m 55.07s , +67d 21m 34.7s) |   C |    20 | 18.8 |        
    7560 | 2021-05-15 15:12:36 |             MASTER- | (10h 02m 17.79s , +67d 23m 17.3s) |   C |    20 | 19.0 |        
    7599 | 2021-05-15 15:13:15 |             MASTER- | (07h 40m 10.37s , +67d 14m 08.1s) |   C |    20 | 18.6 |        
    7632 | 2021-05-15 15:13:47 |             MASTER- | (08h 01m 18.23s , +67d 14m 20.5s) |   C |    20 | 18.6 |        
    7665 | 2021-05-15 15:14:20 |             MASTER- | (07h 21m 33.60s , +78d 36m 34.7s) |   C |    20 | 18.9 |        
    7698 | 2021-05-15 15:14:53 |             MASTER- | (08h 03m 56.87s , +78d 39m 15.3s) |   C |    20 | 18.8 |        
    7731 | 2021-05-15 15:15:26 |             MASTER- | (07h 42m 22.36s , +80d 32m 24.7s) |   C |    20 | 19.1 |        
    7764 | 2021-05-15 15:15:59 |             MASTER- | (06h 38m 32.89s , +72d 49m 57.9s) |   C |    20 | 18.5 |        
    7794 | 2021-05-15 15:16:29 |             MASTER- | (07h 06m 25.08s , +72d 51m 11.3s) |   C |    20 | 18.5 |        
    7825 | 2021-05-15 15:17:01 |             MASTER- | (07h 25m 23.02s , +76d 40m 57.5s) |   C |    20 | 18.6 |        
    7859 | 2021-05-15 15:17:34 |             MASTER- | (08h 01m 31.83s , +76d 45m 16.9s) |   C |    20 | 18.5 |        
   10730 | 2021-05-15 16:05:25 |             MASTER- | (10h 47m 26.58s , +71d 13m 14.3s) |   C |    20 | 17.5 |        
   10761 | 2021-05-15 16:05:56 |             MASTER- | (11h 12m 51.04s , +71d 13m 52.5s) |   C |    20 | 16.4 |        
   10790 | 2021-05-15 16:06:26 |             MASTER- | (11h 06m 11.06s , +73d 07m 32.7s) |   C |    20 | 16.5 |        
   10862 | 2021-05-15 16:07:37 |             MASTER- | (08h 20m 13.12s , +65d 20m 00.6s) |   C |    20 | 14.3 |        
   12631 | 2021-05-15 16:37:06 |             MASTER- | (10h 55m 48.11s , +69d 19m 33.8s) |   C |    20 | 19.0 |        
   12749 | 2021-05-15 16:39:04 |             MASTER- | (10h 47m 19.50s , +71d 11m 10.6s) |   C |    20 | 18.8 |        
   12781 | 2021-05-15 16:39:36 |             MASTER- | (11h 12m 45.39s , +71d 13m 54.5s) |   C |    20 | 18.9 |        
   12812 | 2021-05-15 16:40:07 |             MASTER- | (11h 05m 59.44s , +73d 06m 00.7s) |   C |    20 | 18.9 |        
   12843 | 2021-05-15 16:40:38 |             MASTER- | (11h 34m 22.64s , +73d 09m 07.8s) |   C |    20 | 18.3 |        
   13069 | 2021-05-15 16:44:05 |             MASTER- | (10h 31m 32.67s , +67d 21m 21.2s) |   C |    60 | 12.2 |        
   15372 | 2021-05-15 17:22:27 |   MASTER-Kislovodsk | (08h 37m 26.46s , +73d 46m 54.4s) |   C |    60 | 17.0 |        
   15372 | 2021-05-15 17:22:27 |   MASTER-Kislovodsk | (08h 52m 52.87s , +73d 26m 21.5s) |   C |    60 | 16.8 |        
   15452 | 2021-05-15 17:23:47 |   MASTER-Kislovodsk | (08h 42m 45.82s , +75d 39m 47.1s) |   C |    60 | 17.3 |        
   15452 | 2021-05-15 17:23:47 |   MASTER-Kislovodsk | (09h 00m 17.02s , +75d 19m 28.2s) |   C |    60 | 17.0 |        
   15532 | 2021-05-15 17:25:07 |   MASTER-Kislovodsk | (09h 30m 46.64s , +73d 46m 12.3s) |   C |    60 | 17.2 |        
   15532 | 2021-05-15 17:25:07 |   MASTER-Kislovodsk | (09h 46m 26.21s , +73d 25m 04.4s) |   C |    60 | 16.8 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210514A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30018
SUBJECT: GRB 210514A: Swift-BAT refined analysis 
DATE:    21/05/15 17:59:15 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

C. B. Markwardt (GSFC), E. Ambrosi (INAF-IASFPA) S. D. Barthelmy (GSFC), 
H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210514A (trigger #1048372)
(Lien, et al., GCN Circ. 30009).  The BAT ground-calculated position is
RA, Dec = 2.947, -21.898 deg which is 
  RA(J2000)  =  00h 11m 47.2s 
  Dec(J2000) = -21d 53' 54.0" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.

The mask-weighted light curve showed a complex structure of five main peaks
with sub-peaks.  Emission started around T-1 sec and continued to T+75 sec.
T90 (15-350 keV) is 70.21 +- 0.74 sec (estimated error including systematics).

The time-averaged spectrum from T-1.08 to T+75.13 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.65 +- 0.04.  The fluence in the 15-150 keV band is 7.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.52 sec in the 15-150 keV band
is 8.7 +- 0.4 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1048372/BA/


GRB_name: GRB210515B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30019
SUBJECT: Fermi GRB 210515B: Global MASTER-Net observations report 
DATE:    21/05/15 18:31:04 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210515B ( Fermi GBM team, GCN 30016) errorbox  11999 sec after notice time and 12030 sec after trigger time at 2021-05-15 18:17:16 UT, with upper limit up to  16.6 mag. Observations started at twilight.  The observations began at zenith distance = 80 deg. The sun  altitude  is -16.8 deg. 

The galactic latitude b = -0 deg., longitude l = 87 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1613711

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     109 | 2021-05-15 14:58:25 |             MASTER- | (21h 06m 02.23s , +47d 23m 09.8s) |   C |    20 | 16.2 |        
     184 | 2021-05-15 14:59:35 |             MASTER- | (21h 04m 42.79s , +45d 59m 02.9s) |   C |    30 | 16.4 |        
    1302 | 2021-05-15 15:18:17 |             MASTER- | (21h 04m 33.28s , +45d 13m 33.8s) |   C |    20 | 16.8 |        
    1332 | 2021-05-15 15:18:48 |             MASTER- | (21h 15m 40.72s , +45d 11m 58.3s) |   C |    20 | 16.6 |        
    1363 | 2021-05-15 15:19:18 |             MASTER- | (21h 04m 09.82s , +47d 06m 43.4s) |   C |    20 | 16.4 |        
    1425 | 2021-05-15 15:20:20 |             MASTER- | (20h 43m 07.59s , +45d 15m 09.1s) |   C |    20 | 17.2 |        
    1455 | 2021-05-15 15:20:51 |             MASTER- | (20h 54m 22.64s , +45d 12m 47.8s) |   C |    20 | 17.0 |        
    1486 | 2021-05-15 15:21:21 |             MASTER- | (21h 06m 08.80s , +43d 18m 34.5s) |   C |    20 | 17.0 |        
    1546 | 2021-05-15 15:22:22 |             MASTER- | (20h 41m 56.56s , +47d 07m 21.0s) |   C |    20 | 17.0 |        
    1579 | 2021-05-15 15:22:54 |             MASTER- | (20h 53m 41.36s , +47d 06m 37.3s) |   C |    20 | 16.8 |        
    1609 | 2021-05-15 15:23:25 |             MASTER- | (21h 05m 07.73s , +48d 59m 53.2s) |   C |    20 | 17.2 |        
    2226 | 2021-05-15 15:33:42 |             MASTER- | (21h 04m 28.00s , +45d 14m 10.8s) |   C |    20 | 16.9 |        
    2258 | 2021-05-15 15:34:14 |             MASTER- | (21h 15m 48.32s , +45d 12m 24.6s) |   C |    20 | 17.2 |        
    2291 | 2021-05-15 15:34:47 |             MASTER- | (21h 04m 05.16s , +47d 06m 15.7s) |   C |    20 | 16.6 |        
    2323 | 2021-05-15 15:35:19 |             MASTER- | (21h 15m 48.75s , +47d 05m 58.6s) |   C |    20 | 17.0 |        
    2389 | 2021-05-15 15:36:24 |             MASTER- | (20h 54m 24.69s , +45d 13m 15.4s) |   C |    20 | 17.4 |        
    2422 | 2021-05-15 15:36:58 |             MASTER- | (21h 06m 17.95s , +43d 20m 01.6s) |   C |    20 | 17.1 |        
    2484 | 2021-05-15 15:37:59 |             MASTER- | (20h 41m 59.09s , +47d 10m 00.2s) |   C |    20 | 17.0 |        
    2513 | 2021-05-15 15:38:29 |             MASTER- | (20h 53m 44.11s , +47d 08m 10.4s) |   C |    20 | 16.9 |        
    2547 | 2021-05-15 15:39:03 |             MASTER- | (21h 05m 06.54s , +49d 00m 25.3s) |   C |    20 | 17.4 |        
    2638 | 2021-05-15 15:40:34 |             MASTER- | (20h 56m 26.27s , +43d 19m 00.9s) |   C |    20 | 17.8 |        
    3137 | 2021-05-15 15:48:52 |             MASTER- | (21h 04m 33.72s , +45d 13m 21.3s) |   C |    20 | 16.5 |        
    3166 | 2021-05-15 15:49:22 |             MASTER- | (21h 15m 51.63s , +45d 13m 45.9s) |   C |    20 | 17.0 |        
    3200 | 2021-05-15 15:49:56 |             MASTER- | (21h 04m 08.23s , +47d 07m 58.2s) |   C |    20 | 15.9 |        
    3230 | 2021-05-15 15:50:26 |             MASTER- | (21h 15m 46.86s , +47d 08m 12.0s) |   C |    20 | 16.7 |        
    3291 | 2021-05-15 15:51:27 |             MASTER- | (20h 54m 23.31s , +45d 13m 44.7s) |   C |    20 | 16.7 |        
    3324 | 2021-05-15 15:52:00 |             MASTER- | (21h 06m 19.64s , +43d 19m 16.3s) |   C |    20 | 16.7 |        
    3386 | 2021-05-15 15:53:01 |             MASTER- | (20h 42m 04.44s , +47d 09m 14.9s) |   C |    20 | 16.2 |        
    3415 | 2021-05-15 15:53:31 |             MASTER- | (20h 53m 46.50s , +47d 09m 36.7s) |   C |    20 | 16.8 |        
    3448 | 2021-05-15 15:54:04 |             MASTER- | (21h 05m 10.58s , +49d 02m 10.8s) |   C |    20 | 15.1 |        
    3509 | 2021-05-15 15:55:05 |             MASTER- | (20h 45m 38.00s , +43d 21m 30.8s) |   C |    20 | 16.5 |        
    3539 | 2021-05-15 15:55:34 |             MASTER- | (20h 56m 26.18s , +43d 19m 46.8s) |   C |    20 | 16.3 |        
   12061 | 2021-05-15 18:17:16 |   MASTER-Kislovodsk | (21h 05m 23.40s , +44d 55m 15.5s) |   C |    60 | 15.6 |        
   12061 | 2021-05-15 18:17:16 |   MASTER-Kislovodsk | (21h 10m 52.80s , +44d 29m 34.6s) |   C |    60 | 14.2 |        
   12221 | 2021-05-15 18:19:57 |   MASTER-Kislovodsk | (21h 05m 04.57s , +46d 48m 41.2s) |   C |    60 | 16.3 |        
   12221 | 2021-05-15 18:19:57 |   MASTER-Kislovodsk | (21h 10m 39.76s , +46d 23m 00.4s) |   C |    60 | 16.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210515C
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30020
SUBJECT: GRB 210515C: Swift detection of a burst
DATE:    21/05/15 20:50:24 GMT
FROM:    Antonino D'Ai at IASF-PA  <antonino.dai@inaf.it>

A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), J. A. Kennea (PSU),
K. L. Page (U Leicester), B. Sbarufatti (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 20:02:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a GRB 210515C (trigger=1048618). 
The BAT on-board calculated location is RA, Dec 1.050, -15.011 which is 
  RA(J2000) = 00h 04m 12.00s,
  Dec(J2000) = -15d 00' 39.6"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). 
There is no lightcurve currently available to estimate the duration. 

Using promptly downlinked data we find an uncatalogued X-ray source
located at RA, Dec 1.09221, -14.95325 which is equivalent to:
   RA(J2000)  = 00h 04m 22.13s
   Dec(J2000) = -14d 57' 11.7"
with an uncertainty of 4.9 arcseconds (radius, 90% containment). This
position may be improved as more data are received; the latest position
is available at https://www.swift.ac.uk/sper. No spectrum from the
promptly downlinked event data is yet available to determine the column
density. 

No UVOT data are available at this time. 

Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210515C
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30021
SUBJECT: GRB 210515C: Swift-BAT refined analysis
DATE:    21/05/16 02:01:46 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210515C (trigger #1048618)
(D'Ai et al., GCN Circ. 30020).  The BAT ground-calculated position is
RA, Dec = 1.106, -14.972 deg which is
   RA(J2000)  =  00h 04m 25.4s
   Dec(J2000) = -14d 58' 18.2"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a weak pulse that starts at
~T-3 s, peaks at ~T+1 s, and ends at ~T+11 s, with some tail emission
lasting until ~T+60 s. T90 (15-350 keV) is 55.7 +- 26.7 sec (estimated
error including systematics).

The time-averaged spectrum from T-2.53 to T+56.90 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.26 +- 0.28.  The fluence in the 15-150 keV band is
5.9 +- 1.1 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from
T+0.84 sec in the 15-150 keV band is 0.6 +- 0.2 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1048618/BA/


GRB_name: GRB210515C
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30023
SUBJECT: GRB 210515C: Swift-XRT refined Analysis
DATE:    21/05/16 07:05:16 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), E. Ambrosi 
(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR),
B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), A.P.
Beardmore (U. Leicester) and A. D'Ai report on behalf of the Swift-XRT
team:

We have analysed 7.0 ks of XRT data for GRB 210515C (D'Ai et al. GCN
Circ. 30020), from 76 s to 29.8 ks after the  BAT trigger. The data
comprise 98 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. Using 1614 s of PC mode data and 3 UVOT images, we
find an enhanced XRT position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
1.09417, -14.95334 which is equivalent to:

RA (J2000): 00h 04m 22.60s
Dec(J2000): -14d 57' 12.0"

with an uncertainty of 2.3 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.63 (+0.13, -0.12), followed by a break at T+853 s to
an alpha of 0.57 (+/-0.14).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.06 (+0.24, -0.21). The
best-fitting absorption column is  1.7 (+/-0.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.6 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.11 (+0.26, -0.23)
and a best-fitting absorption column of 6.4 (+5.7, -3.8) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.1 x 10^-11 (3.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.4 (+5.7, -3.8) x 10^20 cm^-2
Galactic foreground: 2.6 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.11 (+0.26, -0.23)

If the light curve continues to decay with a power-law decay index of
0.57, the count rate at T+24 hours will be 3.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x
10^-13 (1.4 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01048618.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210514A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30025
SUBJECT: GRB 210514A: Swift/UVOT Upper Limits
DATE:    21/05/16 15:01:02 GMT
FROM:    Alexander Belles at PSU/Swift  <aub1461@psu.edu>

A. Belles (PSU) and E. Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210514A
80 s after the BAT trigger (Ambrosi et al., GCN Circ. 30008).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ. 30011) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           80          229          147            >20.85
u_FC                293          543          245            >20.12
white               573         1366          225            >21.00
v                      622         1415           97            >18.87
b                     548         1342           77            >19.73
u                     696         5458          210            >19.99
w1                  672         5299          278            >19.59
m2                  646         1440           97            >18.41
w2                  598         1391           97            >18.52

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.022 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210504A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30027
SUBJECT: GRB 210504A: LCO Optical Afterglow Detection
DATE:    21/05/16 17:00:44 GMT
FROM:    Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 210504A (Beardmore, et al., GCN 29929) with the LCO 1-m Sinistro instrument at the South African Astronomical Observatory site, on May 5, from 18:49 to 18:56 UT (corresponding to 4.92 to 5.03 hours from the GRB trigger time) with the Bessel R filter.

We performed a series of 3x180s exposures in R. We detect an uncatalogued optical source in the coadded images consistent with the UVOT position (Breeveld, et al., GCN 29933).  Using the USNO-B.1 catalog as reference, we calculate the following magnitude:

R=20.29+/-0.18

These magnitudes are not corrected for galactic extinction.

R.S. is funded by NSF AST grant #1831682


GRB_name: GRB210515C
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30028
SUBJECT: GRB 210515C: LCO Optical Upper Limit
DATE:    21/05/16 17:02:11 GMT
FROM:    Robert Strausbaugh at U. of the Virgin Islands  <robert.strausbaugh@uvi.edu>

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 210515C (D'Ai, et al., GCN 30020) with the LCO 1-m Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on May 16, from 09:37 to 09:51 UT (corresponding to 13.58 to 13.82 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 3x130s exposures in R and I. We do not detect an uncatalogued optical source in the coadded images in the XRT enhanced error region (Osborne, et al., GCN 30023).  Using the USNO-B.1 catalog as reference, we calculate the following upper limits:

R>21.47

I>20.62

These magnitudes are not corrected for galactic extinction.

R.S. is funded by NSF AST grant #1831682


GRB_name: GRB210516A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30030
SUBJECT: GRB 210516A: Fermi GBM Final Real-time Localization
DATE:    21/05/16 23:44:53 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 23:34:46 UT on 16 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210516A (trigger 642900891.497152 / 210516982).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 22.1, Dec = 74.9 (J2000 degrees, equivalent to J2000 01h 28m, 74d 54'), with a statistical uncertainty of 9.5 degrees.

The angle from the Fermi LAT boresight is 116.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210516982/quicklook/glg_skymap_all_bn210516982.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210516982/quicklook/glg_healpix_all_bn210516982.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210516982/quicklook/glg_lc_medres34_bn210516982.gif


GRB_name: GRB210516A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30031
SUBJECT: Fermi GRB 210516A: Global MASTER-Net observations report 
DATE:    21/05/17 01:30:45 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210516A ( Fermi GBM team, GCN 30030) errorbox  259 sec after notice time and 487 sec after trigger time at 2021-05-16 23:42:54 UT, with upper limit up to  18.9 mag. The observations began at zenith distance = 46 deg. The sun  altitude  is -18.2 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210516A errorbox  488 sec after notice time and 716 sec after trigger time at 2021-05-16 23:46:43 UT, with upper limit up to  16.6 mag. The observations began at zenith distance = 76 deg. The sun  altitude  is -39.6 deg. 

The galactic latitude b = 13 deg., longitude l = 126 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1614502

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     518 | 2021-05-16 23:42:54 |   MASTER-Kislovodsk | (23h 15m 03.42s , +69d 42m 01.8s) |   C |    60 | 18.4 |        
     518 | 2021-05-16 23:42:54 |   MASTER-Kislovodsk | (23h 26m 27.46s , +69d 17m 00.5s) |   C |    60 | 18.9 |        
     747 | 2021-05-16 23:46:43 |          MASTER-IAC | (01h 13m 32.54s , +75d 01m 36.1s) |   C |    60 | 16.4 |        
     747 | 2021-05-16 23:46:43 |          MASTER-IAC | (00h 42m 15.68s , +75d 06m 55.3s) |   C |    60 | 16.5 |        
     827 | 2021-05-16 23:48:03 |          MASTER-IAC | (01h 41m 31.86s , +75d 08m 25.6s) |   C |    60 | 16.5 |        
     827 | 2021-05-16 23:48:03 |          MASTER-IAC | (02h 12m 50.85s , +75d 03m 26.4s) |   C |    60 | 16.5 |        
     907 | 2021-05-16 23:49:23 |          MASTER-IAC | (01h 30m 06.63s , +73d 13m 06.1s) |   C |    60 | 16.1 |        
     907 | 2021-05-16 23:49:23 |          MASTER-IAC | (01h 57m 55.08s , +73d 07m 53.3s) |   C |    60 | 16.0 |        
    1231 | 2021-05-16 23:54:47 |          MASTER-IAC | (01h 21m 05.39s , +71d 20m 06.8s) |   C |    60 | 15.8 |        
    1231 | 2021-05-16 23:54:47 |          MASTER-IAC | (01h 46m 10.92s , +71d 14m 39.4s) |   C |    60 | 15.6 |        
    1311 | 2021-05-16 23:56:07 |          MASTER-IAC | (00h 48m 31.14s , +77d 00m 11.2s) |   C |    60 | 16.6 |        
    1311 | 2021-05-16 23:56:07 |          MASTER-IAC | (01h 24m 15.07s , +76d 54m 58.6s) |   C |    60 | 16.6 |        
    1391 | 2021-05-16 23:57:27 |          MASTER-IAC | (01h 56m 32.02s , +77d 00m 11.0s) |   C |    60 | 16.6 |        
    1391 | 2021-05-16 23:57:27 |          MASTER-IAC | (02h 32m 15.68s , +76d 55m 25.7s) |   C |    60 | 16.6 |        
    1483 | 2021-05-16 23:58:59 |   MASTER-Kislovodsk | (23h 14m 58.41s , +69d 41m 17.7s) |   C |    60 | 18.4 |        
    1483 | 2021-05-16 23:58:59 |   MASTER-Kislovodsk | (23h 26m 24.26s , +69d 15m 49.7s) |   C |    60 | 18.8 |        
    2445 | 2021-05-17 00:15:01 |   MASTER-Kislovodsk | (23h 15m 03.39s , +69d 44m 01.9s) |   C |    60 | 18.1 |        
    2445 | 2021-05-17 00:15:01 |   MASTER-Kislovodsk | (23h 26m 33.43s , +69d 17m 56.9s) |   C |    60 | 18.5 |        
    3166 | 2021-05-17 00:27:02 |   MASTER-Kislovodsk | (02h 34m 16.56s , +81d 02m 00.0s) |   C |    60 | 17.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210517A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30032
SUBJECT: GRB 210517A: Swift detection of a burst
DATE:    21/05/17 05:52:10 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

V. D'Elia (SSDC & INAF-OAR), E. Ambrosi (INAF-IASFPA),
A. D'Ai (INAF-IASFPA), J.D. Gropp (PSU), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL),
B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 05:28:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210517A (trigger=1048783).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 358.174, -39.105 which is 
   RA(J2000) = 23h 52m 42s
   Dec(J2000) = -39d 06' 17"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT lightcurve shows a peak at least
2 seconds long and a maximum count rate of ~2200 counts/s (15-350 keV). 

The XRT began observing the field at 05:29:08.6 UT, 67.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 358.2245,
-39.1020 which is equivalent to:
   RA(J2000)  = 23h 52m 53.88s
   Dec(J2000) = -39d 06' 07.2"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 141 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.30 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.2
(+2.58/-2.26) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 69 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.011. 

Burst Advocate for this burst is V. D'Elia (valerio.delia AT ssdc.asi.it). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210517A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30033
SUBJECT: Swift GRB 210517A: Global MASTER-Net observations report 
DATE:    21/05/17 06:12:17 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB210517.23 (trigger No 1048783,23h 52m 41.76s , -39d 06m 18.0s, R=0.05) errorbox  40 sec after notice time and 254 sec after trigger time at 2021-05-17 05:32:16 UT, with upper limit up to  16.2 mag. The observations began at zenith distance = 83 deg. The sun  altitude  is -71.9 deg. 

The galactic latitude b = -73 deg., longitude l = 344 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1614656

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

     280 |         MASTER-OAFA |   C |    50 | 16.2 |        
     486 |         MASTER-OAFA |   C |    90 | 15.4 |        
     784 |         MASTER-OAFA |   C |   140 | 15.8 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210517A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30034
SUBJECT: GRB 210517A: Enhanced Swift-XRT position
DATE:    21/05/17 09:10:44 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1271 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 210517A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 358.22445, -39.10218 which is equivalent
to:

RA (J2000): 23h 52m 53.87s
Dec (J2000): -39d 06' 07.9"

with an uncertainty of 2.2 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210514A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30035
SUBJECT: GRB 210514A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/05/17 10:10:30 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

T. Sakamoto, A. Yoshida, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The long bright GRB 210514A (Swift detection: Ambrosi et al., GCN Circ.
30008, Lien and Ambrosi, GCN Circ. 30009, Markwardt et al., GCN Circ.
30018; https://gcn.gsfc.nasa.gov/other/210514A.gcn3) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 18:23:42.591 UTC on 14 May 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1305051705/index.html).
The burst signal was seen by all CGBM detectors.

The burst light curve shows several partially overlapped pulses which
start at T+3.3 sec, peak at T+4.9 sec, and end at T+53.8 sec.
The T90 and T50 durations measured by the SGM data are 46.0 +- 2.5 sec
and 25.9 +- 3.3 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1305051705/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210517A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30036
SUBJECT: GRB 210517A: AGILE detection
DATE:    21/05/17 12:32:54 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), C. Pittori (SSDC, and INAF/OAR), G. Piano (INAF/IAPS),
M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo,
C. Casentini, Y. Evangelista (INAF/IAPS), F. Lucarelli, F. Verrecchia
(SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano,  V. Fioretti, F.
Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi
(INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois
(INAF/OA-Cagliari), I. Donnarumma (ASI), F. Longo (Univ. Trieste and INFN
Trieste), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:

The AGILE satellite detected the long GRB 210517A at T0 = 2021-05-17
05:28:01 s (UTC), reported by Swift (GCNs #30032, #30034).

The burst is visible in the AGILE scientific ratemeters of the SuperAGILE
(SA; 20-60 keV) and MiniCALorimeter (MCAL; 0.4-100 MeV) detectors. The
event lasted ~6 s and released a total number of 663 counts in the SA
detector (above a background rate of 77 Hz) and 8759 counts in the MCAL
detector (above a background rate of 1200 Hz). The AGILE ratemeter light
curves can be found at
http://www.agilescienceapp.it/notices/GRB210517A_AGILE_RM.png .

Additional analysis of AGILE data is in progress.


GRB_name: GRB210517A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30037
SUBJECT: GRB 210517A: VLT/X-shooter optical afterglow and redshift
DATE:    21/05/17 13:07:00 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>

N. R. Tanvir (Univ. Leicester), D. Xu (NAOC/CAS), L. Izzo (DARK/NBI), D. 
A. Kann (HETH/IAA-CSIC), D. B. Malesani (DTU space), J.-B. Vielfaure 
(APC), P. Jakobsson (Univ. Iceland), A. de Ugarte Postigo (HETH/IAA-CSIC 
and DARK/NBI), K. E. Heintz (Univ. Iceland and DAWN/NBI), V. D'Elia 
(ASI/SSDC), A. J. Levan (Radboud Univ.), S. D. Vergani (CNRS, Paris 
Obs.), S. Campana (INAF/Brera), G. Pugliese (Amsterdam), report on 
behalf of the Stargate collaboration:

We observed the field of GRB 210517A (D'Elia et al., GCN 30032; Ursi et 
al., GCN 30036) using the ESO VLT UT3 (Melipal) equipped with the 
X-shooter spectrograph. Our spectra cover the wavelength range 
3000-21000 AA, and consist of 4 exposures by 600 s each. The observation 
mid time was 2021 May 17.387 UT (3.82 hr after the GRB).

In a 30 s image taken with the acquisition camera on May 17.364 UT, we 
detect a single object consistent with the UVOT-enhanced XRT position 
(Beardmore et al., GCN 30034), at J2000 coordinates:

RA = 23:52:53.95
Dec = -39:06:08.3

We measure for this target an AB magnitude r = 22.3 +- 0.1 (calibrated 
against the Legacy Survey, but only very few, faint stars are present in 
the acquisition camera field of view). We note that at the same 
position, to within the uncertainties, there is a faint object visible 
in the Legacy Survey, with AB magnitude r ~ 23.7. We conclude that the 
above source is the optical afterglow of GRB 210517A, and the archival 
object is its host galaxy.

In our spectra, continuum is detected over the whole observed range. A 
prominent emission line is detected around 4236 AA, which we identify as 
Ly alpha in emission. This interpretation is confirmed by the detection 
of both emission lines in the near-infrared arm (corresponding to [O II] 
and [O III]), and a plethora of metallic absorption features, among them 
Si II, Si IV, O I, C IV, C II, all at a common redshift z = 2.486. 
Consistent with the detection of bright Ly alpha in emission, the 
observed HI absorption column density is low.

We note that at z = 2.486 the galaxy is a particularly bright GRB host, 
with an absolute AB magnitude M(1800 AA) ~ -21.5.

We acknowledge excellent support from the ESO observing staff in 
Paranal, in particular Luca Sbordone, Francisco Caceres, and Boris 
Haeussler.


GRB_name: GRB210515C
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30039
SUBJECT: GRB 210515C: Swift/UVOT Upper Limits
DATE:    21/05/17 17:35:31 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210515C: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and A. D'Ai (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210515C
40 s after the BAT trigger (A. D'Ai et al., GCN Circ. 30020).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 30023)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

b                      486            851            58      >18.60
uvm2                758           5041         216       >18.99
u                      231           5285         311       >19.33
v                      561           4836         235       >18.60
uvw1                610           5246         235        >18.89
uvw2              4432           4631         196        >18.90
white                 72             942         271        >20.12


The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.011 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210517A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30040
SUBJECT: GRB 210517A: Swift/UVOT Upper Limits
DATE:    21/05/17 17:35:58 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210517A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and V. D'Elia (SSDC & INAF-OAR)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210517A
69 s after the BAT trigger (D'Elia et al., GCN Circ. 30032).
No optical afterglow consistent with the optical position
(Tanvir et al. GCN Circ. 30037)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            69          219          147         >19.4
u_FC               282          531          246         >19.7
white               69         1356          373         >19.9
v                  611         5047          274         >19.0
b                  537         1332           78         >19.5
u                  282         1307          304         >19.7
w1                 661         1109           39         >18.4
m2                5052         5070           18         >18.7
w2                4642         4841          197         >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.011 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210517A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30042
SUBJECT: GRB 210517A: Swift-XRT refined Analysis
DATE:    21/05/17 19:21:45 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

K.L. Page (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &
INAF-OAR), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea (PSU),
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and V. D'Elia
report on behalf of the Swift-XRT team:

We have analysed 7.7 ks of XRT data for GRB 210517A (D'Elia et al. GCN
Circ. 30032), from 85 s to 40.6 ks after the  BAT trigger. The data are
entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Beardmore et al. (GCN Circ. 30034).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.90 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.71 (+0.18, -0.14). The
best-fitting absorption column is  1.4 (+7.0, -1.4) x 10^21 cm^-2, at a
redshift of 2.486, in addition to the Galactic value of 1.3 x 10^20
cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum  is 3.7 x
10^-11 (3.9 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 1.3 x 10^20 cm^-2
Intrinsic column:    1.4 (+7.0, -1.4) x 10^21 cm^-2 at z=2.486
Photon index:      1.71 (+0.18, -0.14)

If the light curve continues to decay with a power-law decay index of
0.90, the count rate at T+24 hours will be 3.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (1.2 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01048783.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210517A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30043
SUBJECT: GRB 210517A: Swift-BAT refined analysis
DATE:    21/05/17 20:06:05 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),  V. D'Elia (SSDC & INAF-OAR), 
H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+659 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210517A (trigger #1048783)
(D'Elia, et al., GCN Circ. 30032).  The BAT ground-calculated position is
RA, Dec = 358.190, -39.104 deg which is 
   RA(J2000)  =  23h 52m 45.5s 
   Dec(J2000) = -39d 06' 15.0" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.

The mask-weighted light curve shows a single peak of three-second duration
near the trigger time.  T90 (15-350 keV) is 3.06 +- 1.4 sec (estimated error including 
systematics).

The time-averaged spectrum from T-0.17 to T+3.13 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.85 +- 0.25.  The fluence in the 15-150 keV band is 1.5 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.18 sec in the 15-150 keV band
is 1.5 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The position of this burst on the BAT T90-Hardness diagram suggests that it is a 
long GRB.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1048783/BA/


GRB_name: GRB210518A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30045
SUBJECT: GRB 210518A: Fermi GBM Final Real-time Localization
DATE:    21/05/18 13:15:25 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 13:04:09 UT on 18 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210518A (trigger 643035854.639946 / 210518545).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 270.0, Dec = 49.6 (J2000 degrees, equivalent to J2000 18h 00m, 49d 36'), with a statistical uncertainty of 1.8 degrees.

The angle from the Fermi LAT boresight is 142.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210518545/quicklook/glg_skymap_all_bn210518545.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210518545/quicklook/glg_healpix_all_bn210518545.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210518545/quicklook/glg_lc_medres34_bn210518545.gif


GRB_name: GRB210514A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30048
SUBJECT: Konus-Wind detection of GRB 210514A
DATE:    21/05/18 18:03:52 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The long-duration GRB 210514A
(Swift-BAT detection: Ambrosi et al., GCN 30008;
Lien & Ambrosi, GCN 30009; Markwardt et al., GCN 30018;
CALET-CGBM detection: Sakamoto et al., GCN 30035)
triggered Konus-Wind at T0=66225.021 s UT (18:23:45.021).

The burst light curve shows a multipeaked structure
started at ~T0-0.3 s with a total duration of ~74.2 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210514_T66225/

As observed by Konus-Wind, the burst
had a fluence of 1.97(-0.43,+0.56)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.168 s,
of 6.70(-3.12,+3.85)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+49.408 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.38(-0.40,+0.88),
the high energy photon index beta = -2.27(-0.42,+0.23),
the peak energy Ep = 118(-24,+40) keV
(chi2 = 66/55 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.42(-0.53,+1.22),
the high energy photon index beta = -2.26(2.26,+0.39),
the peak energy Ep = 204(-82,+113) keV
(chi2 = 57/55 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB210518A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30049
SUBJECT: Fermi GRB 210518A: Global MASTER-Net observations report 
DATE:    21/05/18 19:41:21 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Tavrida robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 210518A ( Fermi GBM team, GCN 30045) errorbox  21119 sec after notice time and 21211 sec after trigger time at 2021-05-18 18:57:41 UT, with upper limit up to  17.5 mag. Observations started at twilight.  The observations began at zenith distance = 48 deg. The sun  altitude  is -16.4 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210518A errorbox  22517 sec after notice time and 22609 sec after trigger time at 2021-05-18 19:20:59 UT, with upper limit up to  18.9 mag. The observations began at zenith distance = 44 deg. The sun  altitude  is -22.7 deg. 

The galactic latitude b = 28 deg., longitude l = 77 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1615984

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   21242 | 2021-05-18 18:57:41 |      MASTER-Tavrida | (17h 48m 41.51s , +49d 49m 53.4s) |   C |    60 | 14.3 |        
   21321 | 2021-05-18 18:59:00 |      MASTER-Tavrida | (17h 44m 23.63s , +51d 42m 07.4s) |   C |    60 | 17.0 |        
   21401 | 2021-05-18 19:00:20 |      MASTER-Tavrida | (17h 57m 38.57s , +51d 41m 50.7s) |   C |    60 | 17.5 |        
   21482 | 2021-05-18 19:01:41 |      MASTER-Tavrida | (17h 59m 42.95s , +45d 59m 33.9s) |   C |    60 | 17.1 |        
   22181 | 2021-05-18 19:13:20 |      MASTER-Tavrida | (17h 42m 50.03s , +47d 56m 08.8s) |   C |    60 | 16.6 |        
   22260 | 2021-05-18 19:14:40 |      MASTER-Tavrida | (18h 01m 23.46s , +49d 48m 32.6s) |   C |    60 | 16.0 |        
   22340 | 2021-05-18 19:15:59 |      MASTER-Tavrida | (17h 53m 46.00s , +47d 53m 44.4s) |   C |    60 | 15.3 |        
   22419 | 2021-05-18 19:17:19 |      MASTER-Tavrida | (18h 05m 59.67s , +47d 53m 29.1s) |   C |    60 | 17.0 |        
   22499 | 2021-05-18 19:18:38 |      MASTER-Tavrida | (17h 48m 41.80s , +49d 49m 37.4s) |   C |    60 | 15.4 |        
   22578 | 2021-05-18 19:19:57 |      MASTER-Tavrida | (17h 44m 22.63s , +51d 42m 38.2s) |   C |    60 | 15.7 |        
   22640 | 2021-05-18 19:20:59 |   MASTER-Kislovodsk | (18h 21m 01.98s , +50d 40m 53.5s) |   C |    60 | 18.0 |        
   22720 | 2021-05-18 19:22:19 |   MASTER-Kislovodsk | (17h 45m 12.19s , +46d 54m 06.1s) |   C |    60 | 18.1 |        
   22720 | 2021-05-18 19:22:19 |   MASTER-Kislovodsk | (17h 51m 09.20s , +46d 29m 59.0s) |   C |    60 | 18.9 |        
   22737 | 2021-05-18 19:22:37 |      MASTER-Tavrida | (17h 59m 37.58s , +46d 00m 28.9s) |   C |    60 | 14.3 |        
   22960 | 2021-05-18 19:26:20 |   MASTER-Kislovodsk | (17h 39m 32.63s , +50d 19m 41.6s) |   C |    60 | 18.9 |        
   23252 | 2021-05-18 19:31:11 |      MASTER-Tavrida | (17h 42m 55.70s , +47d 55m 10.9s) |   C |    60 | 16.3 |        
   23331 | 2021-05-18 19:32:30 |      MASTER-Tavrida | (18h 01m 17.16s , +49d 47m 37.3s) |   C |    60 | 16.2 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210519A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30050
SUBJECT: GRB 210519A: Fermi GBM Final Localization
DATE:    21/05/19 15:38:55 GMT
FROM:    Rachel Dunwoody at UCD  <rachel.dunwoody@ucdconnect.ie>

The Fermi GBM team reports the detection of a likely long GRB.

At 06:38:53.86 UT on 19 May 2021, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 210519A (trigger 643099138 / 210519277).

The on-ground calculated location, using the Fermi GBM trigger data, is RA
= 187.9, Dec = -40.2(J2000 degrees, equivalent to J2000 12h 31m, -40d 12'),
with a statistical uncertainty of 4.3 degrees.

The angle from the Fermi LAT boresight is 75 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210519277/quicklook/glg_skymap_all_bn210519277.png

The HEALPix FITS file, including the estimated localization systematic, can
be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210519277/quicklook/glg_healpix_all_bn210519277.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210519277/quicklook/glg_lc_medres34_bn210519277.gif


GRB_name: GRB210518A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30053
SUBJECT: IPN triangulation of GRB 210518A
DATE:    21/05/19 19:18:30 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

A. Ridnaia, S. Golenetskii, D. Frederiks, D. Svinkin,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The long-duration GRB 210518A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30045)
was detected by Fermi (GBM trigger 643035854), Konus-Wind,
and Mars-Odyssey (HEND) at about 47050 s UT (13:04:10).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
  271.081 (18h 04m 19s) +50.035 (+50d 02' 07")
 Corners:
  288.400 (19h 13m 36s) +51.036 (+51d 02' 11")
  287.357 (19h 09m 26s) +51.489 (+51d 29' 21")
  255.561 (17h 02m 15s) +46.119 (+46d 07' 07")
  256.707 (17h 06m 50s) +46.052 (+46d 03' 09")
 ---------------------------------------------
The error box area is 9.4 sq. deg, and its maximum
dimension is 22.0 deg (the minimum one is 26 arcmin).
The Sun distance was 96 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210518_T47051/IPN

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210519A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30055
SUBJECT: Fermi GRB 210519A: Global MASTER-Net observations report 
DATE:    21/05/19 23:35:36 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210519A ( Fermi GBM team, GCN 30050) errorbox  40250 sec after notice time and 40298 sec after trigger time at 2021-05-19 17:50:32 UT, with upper limit up to  16.7 mag. Observations started at twilight.  The observations began at zenith distance = 78 deg. The sun  altitude  is -12.6 deg. 

MASTER-SAAO robotic telescope  located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 210519A errorbox  58554 sec after notice time and 58602 sec after trigger time at 2021-05-19 22:55:36 UT, with upper limit up to  18.5 mag. The observations began at zenith distance = 43 deg. The sun  altitude  is -77.1 deg. 

The galactic latitude b = 22 deg., longitude l = 299 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1616830

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   40328 | 2021-05-19 17:50:32 |   MASTER-Kislovodsk | (12h 22m 19.71s , -34d 52m 18.4s) |   C |    60 | 14.0 |        
   41150 | 2021-05-19 18:04:13 |   MASTER-Kislovodsk | (12h 40m 51.34s , -34d 52m 59.1s) |   C |    60 | 16.4 |        
   41150 | 2021-05-19 18:04:13 |   MASTER-Kislovodsk | (12h 36m 11.32s , -34d 30m 24.5s) |   C |    60 | 16.7 |        
   41230 | 2021-05-19 18:05:33 |   MASTER-Kislovodsk | (12h 22m 17.46s , -34d 51m 54.8s) |   C |    60 | 16.3 |        
   43450 | 2021-05-19 18:42:34 |   MASTER-Kislovodsk | (12h 40m 49.26s , -34d 51m 23.6s) |   C |    60 | 15.9 |        
   43450 | 2021-05-19 18:42:34 |   MASTER-Kislovodsk | (12h 36m 08.06s , -34d 29m 00.1s) |   C |    60 | 16.3 |        
   43530 | 2021-05-19 18:43:54 |   MASTER-Kislovodsk | (12h 22m 26.48s , -34d 52m 33.3s) |   C |    60 | 15.8 |        
   58633 | 2021-05-19 22:55:36 |         MASTER-SAAO | (12h 35m 09.15s , -40d 27m 20.7s) |   C |    60 | 18.2 |        
   58713 | 2021-05-19 22:56:56 |         MASTER-SAAO | (12h 45m 32.72s , -40d 28m 26.9s) |   C |    60 | 18.5 |        
   58794 | 2021-05-19 22:58:18 |         MASTER-SAAO | (12h 37m 03.01s , -42d 22m 05.2s) |   C |    60 | 18.2 |        
   59083 | 2021-05-19 23:03:06 |         MASTER-SAAO | (12h 47m 51.42s , -42d 23m 06.8s) |   C |    60 | 18.4 |        
   59890 | 2021-05-19 23:16:33 |         MASTER-SAAO | (12h 35m 08.28s , -40d 27m 54.7s) |   C |    60 | 18.4 |        
   59970 | 2021-05-19 23:17:53 |         MASTER-SAAO | (12h 45m 36.10s , -40d 27m 13.1s) |   C |    60 | 18.3 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210517A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30057
SUBJECT: GRB 210517A: KCT optical upper limit
DATE:    21/05/20 06:11:09 GMT
FROM:    Gregory SungHak Paek at SNU  <shpaek@astro.snu.ac.kr>

Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Gu Lim (SNU
ARC/SNU), on behalf of GECKO collaboration

 We searched for the optical counterpart of GRB 210517A (V. E'Elia et al.
GCN #30032) with the 0.36-m class KCT (KIAS Chamnun Telescope) in
DeepSkyChile, one of the facilities of the GW EM-Counterpart Korean
Observatory (GECKO).

 We observed the center of Swift/XRT localization (RA, Dec = 358.2245
-39.1020) +2.94 hours after report, but could not find any possible
transient within the field of view and at the reported location of optical
afterglow (N. R. Tanvir et al. GCN 30037). We calibrated flux with the
APASS catalog and used an AB magnitude system. Depth means 5 sigma upper
limit for a point source detection. The magnitudes are not corrected for
galactic extinction.

------
Filter Date-obs[UT] Exp.time[s] Depth
I 2021-05-17T08:24:35.583 180*3 18.435
R 2021-05-17T08:37:00.750 180*3 19.581
V 2021-05-17T08:49:25.333 180*3 20.005
B 2021-05-17T09:01:50.250 180*3 20.047

Gravitational-wave EM Counterpart Korean Observatory (GECKO) is a network
of 10+ 0.5m to 1m class telescopes over the world.


GRB_name: GRB210520A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30059
SUBJECT: GRB 210520A: Fermi GBM Final Real-time Localization
DATE:    21/05/20 19:17:25 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 19:07:02 UT on 20 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210520A (trigger 643230427.939988 / 210520797).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 147.9, Dec = -67.0 (J2000 degrees, equivalent to J2000 09h 51m, -67d 00'), with a statistical uncertainty of 3.7 degrees.

The angle from the Fermi LAT boresight is 15.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210520797/quicklook/glg_skymap_all_bn210520797.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210520797/quicklook/glg_healpix_all_bn210520797.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210520797/quicklook/glg_lc_medres34_bn210520797.gif


GRB_name: GRB210520A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30060
SUBJECT: Fermi GRB 210520A: Global MASTER-Net observations report 
DATE:    21/05/20 22:50:11 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210520A ( Fermi GBM team, GCN 30059) errorbox  12138 sec after notice time and 12187 sec after trigger time at 2021-05-20 22:30:10 UT, with upper limit up to  17.0 mag. Observations started at twilight.  The observations began at zenith distance = 39 deg. The sun  altitude  is -10.0 deg. 

The galactic latitude b = -14 deg., longitude l = 285 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1617942

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   12218 | 2021-05-20 22:30:10 |         MASTER-OAFA | (09h 02m 19.62s , -69d 42m 16.2s) |   C |    60 | 16.8 |        
   12297 | 2021-05-20 22:31:29 |         MASTER-OAFA | (09h 24m 33.57s , -69d 42m 48.7s) |   C |    60 | 17.0 |        
   12376 | 2021-05-20 22:32:49 |         MASTER-OAFA | (08h 58m 19.03s , -67d 47m 42.0s) |   C |    60 | 17.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210520A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30061
SUBJECT: GRB 210520A: GECAM detection
DATE:    21/05/21 04:54:51 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

C. Zheng, Y. Q. Zhang, S. L. Xiong, S. L. Xie, Y. Huang, S. Xiao, Y. Zhao, 
J. C. Liu, C. Y. Li, W. C. Xue, C. Cai, Z. W. Guo, X. Y. Zhao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, Q. B. Yi,
B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang,
K. Zhang, P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao,  S. J. Zheng,
X. Zhou (IHEP), report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long burst,
GRB 210520A, at 2021-05-20T19:07:03.550 UTC (denoted as T0), 
which was also observed by Fermi/GBM (GCN #30059) and 
INTEGRAL/SPI-ACSï¼ˆTrigID 9218ï¼‰.

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of 
multiple pulses with a duration of about 50s.  

An automatic on-ground localization was calculated using the light curves
and spectrum. Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
ra: 129.04 deg
dec: -72.01 deg
err: 5.55 deg (statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

GECAM location is consistent with the Fermi/GBM(GCN #30059) position within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_75236823.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210520A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30062
SUBJECT: GRB 210520A: Fermi-LAT detection
DATE:    21/05/21 05:15:00 GMT
FROM:    Magnus Axelsson at Stockholm U.  <magaxe@kth.se>

N. Di Lalla (Stanford Univ.), M. Arimoto (Kanazawa Univ.), M. Axelsson (KTH & Stockholm Univ.), D. Kocevski (NASA/MSFC), N. Omodei (Stanford Univ.) report on behalf of the Fermi-LAT Collaboration:

On May 20, 2021 Fermi-LAT detected high-energy emission from GRB 210520A, which was also detected by Fermi-GBM (trigger 643230427.939988 / 210520797, GCN 30059).

The best LAT on-ground location is found to be

(RA, Dec) = 123.0, -69.4 (degrees, J2000)

with an error radius of 0.7 deg (90% containment, statistical error only). This was 21 deg from the LAT boresight at the time of the GBM trigger:

T0 = 19:07:02 UT.

The data from the Fermi-LAT show a significant increase in the event rate after the GBM trigger that is spatially and temporally correlated with the GBM emission (9 degrees from the GBM location) with high significance.

The photon flux above 100 MeV in the time interval 0-100s after the GBM trigger is (2.5 +/- 0.7) e-05 ph/cm2/s.

The estimated photon index above 100 MeV is -2.6 +/- 0.4.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is Niccolo' Di Lalla (niccolo.dilalla@stanford.edu).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.


GRB_name: GRB210520A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30063
SUBJECT: GRB 210520A: Tiled Swift observations
DATE:    21/05/21 06:54:46 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 210520A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00099

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210520A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30065
SUBJECT: GRB 210520A: Fermi GBM detection
DATE:    21/05/21 12:41:47 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P. Veres, B. Hristov and C. Meegan (all UAH) report on behalf of the
Fermi GBM Team:

"At 19:07:02.00 UT on 20 May 2021, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 210520A (trigger 643230427 /
210520797) which was also detected by the Fermi LAT (Di Lalla et al.,
GCN 30062) and GECAM (Zheng et al GCN 30061). The GBM on-ground
location (reported in GCN 30059) is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time is 21 degrees.

The GBM light curve consists of a large number of pulses
with a duration (T90) of about 56 s (50-300 keV).
The time-averaged spectrum from T0-1.3 s to T0+58 s is
adequately fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.18 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 4.4 +/- 1.8 MeV.

The event fluence (10-1000 keV) in this time interval is
(1.02 +/- 0.04)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.58 s in the 10-1000 keV band
is 2.6 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210413B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30066
SUBJECT: GRB210413B: further Swift-XRT observations
DATE:    21/05/21 14:38:33 GMT
FROM:    Antonino D'Ai at IASF-PA  <antonino.dai@inaf.it>

A. Dâ€™Ai (INAF-IASFPA), A. Tohuvavohu (U Toronto) 
and M. H. Siegel (PSU) report on behalf of the Swift team:

Swift-XRT has performed further follow-up observations of the
ground-detected burst GRB 200413B (Tohuvavohu et al. GCN 
Cir. 29819), collecting a total of 9.2 ks of Photon Counting (PC) 
mode data between T0+2.1 days and T0+37 days. 

The uncatalogued candidate X-ray source (Source 1) reported 
in Kennea et al. (GCN Circ. 29827) which had also a possible 
UV counterpart (Siegel, GCN Circ. 29912) is still detected in 
XRT at a count rate consistent with the first observations. 
We thus rule out a possible association with the burst.

The results of the XRT-team automatic analysis are at 
https://www.swift.ac.uk/ToO_GRBs/00021428/

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210521A
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30067
SUBJECT: GRB 210521A: MAXI/GSC detection
DATE:    21/05/21 15:04:39 GMT
FROM:    Motoko Serino at Aoyama Gakuin U.  <serino@phys.aoyama.ac.jp>

S. Yamada (Kyoto U.), H. Negoro, M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.),
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, M. Serino, S. Sugita, K. Komachi, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, M. Niwano, R. Hosokawa (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA),
Y. Ueda, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.),
H. Tsunemi (Osaka U.),
M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU),
M. Sugizaki (NAOC) report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source 
at 13:04:08 UT on 2021 May 21.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (264.674 deg, -61.752 deg) = (17 38 41, -61 45 07) (J2000)
with a 90% C.L. statistical error of 0.12 deg and an additional systematic uncertainty of
0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 508 +- 51 mCrab
(4.0-10.0keV, 1 sigma error).
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (264.912, -61.246) deg = (17 39 38, -61 14 45) (J2000)
(R.A., Dec) = (264.426, -61.253) deg = (17 37 42, -61 15 10) (J2000)
(R.A., Dec) = (264.502, -62.494) deg = (17 38 00, -62 29 38) (J2000)
(R.A., Dec) = (265.008, -62.486) deg = (17 40 01, -62 29 09) (J2000)
There was no significant excess flux in the previous transit at 12:43 UT
and in the next transit at 14:16 UT with an upper limit of 20 mCrab for each.


GRB_name: GRB210520A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30069
SUBJECT: GRB 210520A: Swift-XRT observations
DATE:    21/05/22 10:47:24 GMT
FROM:    Paolo D'Avanzo at INAF - OAB  <paolo.davanzo@inaf.it>

M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai
(INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U.
Toronto), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester)
and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 210520A (Di Lalla et al. GCN Circ. 30062)
in a series of observations tiled on the sky. The total exposure time
is 5.6 ks, distributed over 19 tiles; the maximum exposure at a single
sky location was 649 s. The data were collected between T0+43.1 ks and
T0+62 ks, and are entirely in Photon Counting (PC) mode. 

Two uncatalogued X-ray sources are detected above the RASS 3-sigma
upper limit at this position, matching the afterglow criteria. However,
none of them shows definitive signs of fading, and both of them are
consistent with 2MASS objects within the XRT error circle. Therefore,
none of them is likely the afterglow.

Details of these sources are given below:

Source 2:
  RA (J2000):  122.12040 = 08:08:28.90
  Dec (J2000): -69.7668 = -69:46:00.5
  Error: 7.7 arcsec (radius, 90% conf.)
  Count-rate: (1.95 [+1.19, -0.85])e-2 ct s^-1  
  Distance: 28.7' from Fermi/LAT position.

Source 3:
  RA (J2000):  124.47176 =  08:17:53.22
  Dec (J2000): -69.2963  =  -69:17:46.8
  Error: 8.6 arcsec (radius, 90% conf.)
  Count-rate: (3.0 [+1.6, -1.1])e-2 ct s^-1  
  Distance: 31.8' from Fermi/LAT position.

The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00099.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210522A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30070
SUBJECT: GRB 210522A: GECAM detection
DATE:    21/05/23 16:33:25 GMT
FROM:    Shuo Xiao at IHEP  <xiaoshuo@ihep.ac.cn>

C. Y. Li, S. Xiao, S. L. Xiong, X. Y. Zhao, X. Y. Song, Y. Huang,
C. Cai, Y. Zhao, Q. B. Yi, J. C. Liu, Y. Q. Zhang, W. C. Xue, C. Zheng,
Z. W. Guo, X. L. Zhao, B. X. Zhang, C. W. Wang, S. L. Xie,
P. Wang, X. B. Li, W. X. Peng, R. Qiao, J. Wang, H. S. Zhao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long hard GRB,
GRB 210522A, at 2021-05-22T22:11:44.450 UTC (denoted as T0), 
which was also observed by CALET/GBM, INTEGRAL/SPI-ACS and Konus-WIND.

According to the GECAM-B light curves in about 8 keV-4 MeV, 
this burst mainly consists of multiple pulses with a duration of about 50s.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_grd_75420704.45.png

GECAM-B localized this burst to the following position (J2000):
Ra: 90.06 deg
Dec: 1.36 deg
Err: 1.19 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

In addition, we derived a triangulation location for this burst using
GECAM-B data together with public data of INTEGRAL-SPI/ACS and Konus-WIND,
based on a novel method (S. Xiao, et al., submitted). 
Although there are two intersection regions of triangulation annuli, only one
region is consistent with the above location given by GECAM-B alone, thus is
the final location region (3-sigma), which could be defined as (J2000):
        Ra (deg)  Dec (deg)
Center  85.78, 2.09
Corner
        83.67, 0.30
        79.45, 2.09
        90.00, 2.69
        87.89, 3.88

The location map could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/location_gecamb_grd_75420704.png

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).

We are very grateful for the public data of INTEGRAL-SPI/ACS and Konus-WIND.


GRB_name: GRB210524A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30071
SUBJECT: GRB 210524A: Fermi GBM Final Real-time Localization
DATE:    21/05/24 05:10:21 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 04:59:59 UT on 24 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210524A (trigger 643525204.091768 / 210524208).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 337.3, Dec = -47.0 (J2000 degrees, equivalent to J2000 22h 29m, -47d 00'), with a statistical uncertainty of 1.5 degrees.

The angle from the Fermi LAT boresight is 65.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210524208/quicklook/glg_skymap_all_bn210524208.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210524208/quicklook/glg_healpix_all_bn210524208.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210524208/quicklook/glg_lc_medres34_bn210524208.gif


GRB_name: GRB210524A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30072
SUBJECT: Fermi GRB 210524A: Global MASTER-Net observations report 
DATE:    21/05/24 05:32:00 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210524A ( Fermi GBM team, GCN 30071) errorbox  559 sec after notice time and 597 sec after trigger time at 2021-05-24 05:09:56 UT, with upper limit up to  17.0 mag. Observations started at twilight.  The observations began at zenith distance = 81 deg. The sun  altitude  is -12.3 deg. 

The galactic latitude b = -56 deg., longitude l = 348 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1620119

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     657 | 2021-05-24 05:09:56 |          MASTER-IAC | (22h 28m 27.06s , -47d 09m 06.7s) |  P| |   120 | 16.8 |        
     657 | 2021-05-24 05:09:56 |          MASTER-IAC | (22h 27m 16.27s , -47d 03m 27.4s) |  P- |   120 | 16.4 |        
     812 | 2021-05-24 05:12:16 |          MASTER-IAC | (22h 28m 21.78s , -47d 10m 15.3s) |  P| |   150 | 17.0 |        
     812 | 2021-05-24 05:12:16 |          MASTER-IAC | (22h 27m 11.27s , -47d 04m 34.4s) |  P- |   150 | 16.6 |        
     997 | 2021-05-24 05:15:06 |          MASTER-IAC | (22h 28m 27.57s , -47d 09m 54.6s) |  P| |   180 | 16.9 |        
     997 | 2021-05-24 05:15:06 |          MASTER-IAC | (22h 27m 17.33s , -47d 04m 12.7s) |  P- |   180 | 16.5 |        
    1197 | 2021-05-24 05:18:26 |          MASTER-IAC | (22h 28m 24.64s , -47d 08m 43.0s) |  P| |   180 | 16.7 |        
    1197 | 2021-05-24 05:18:26 |          MASTER-IAC | (22h 27m 14.65s , -47d 03m 01.0s) |  P- |   180 | 16.2 |        
    1397 | 2021-05-24 05:21:45 |          MASTER-IAC | (22h 28m 24.73s , -47d 10m 02.6s) |  P| |   180 | 16.4 |        
    1397 | 2021-05-24 05:21:45 |          MASTER-IAC | (22h 27m 14.82s , -47d 04m 19.1s) |  P- |   180 | 15.9 |        


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210524A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30073
SUBJECT: GRB 210524A: BALROG localization (Fermi Trigger 643525204 / GRB 210524208)
DATE:    21/05/24 10:13:22 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
643525204 at 04:59:59 on 24 May 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 343.2+/-0.7 deg
Decl.(2000.0) = -47.2+/-0.4 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210524208/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210524208/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210524208/json

                        


GRB_name: GRB210524B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30074
SUBJECT: GRB 210524B: Fermi GBM Final Real-time Localization
DATE:    21/05/24 11:30:50 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 11:20:34 UT on 24 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210524B (trigger 643548039.686002 / 210524473).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 148.5, Dec = 7.8 (J2000 degrees, equivalent to J2000 09h 54m, 7d 47'), with a statistical uncertainty of 4.8 degrees.

The angle from the Fermi LAT boresight is 92.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210524473/quicklook/glg_skymap_all_bn210524473.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210524473/quicklook/glg_healpix_all_bn210524473.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210524473/quicklook/glg_lc_medres34_bn210524473.gif


GRB_name: GRB210524A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30076
SUBJECT: IPN triangulation of GRB 210524A
DATE:    21/05/25 10:03:18 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The intense, long-duration GRB 210524A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30071;
BALROG localization: Biltzinger et al., GCN Circ. 30073)
was detected by Fermi (GBM trigger 643525204), Konus-Wind,
Mars-Odyssey (HEND), INTEGRAL (SPI-ACS), and Swift-BAT
at about 17999 s UT (04:59:59).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   343.564 (22h 54m 15s) -46.672 (-46d 40' 19")
  Corners:
   342.645 (22h 50m 35s) -49.867 (-49d 52' 00")
   344.262 (22h 57m 03s) -43.354 (-43d 21' 13")
   344.203 (22h 56m 49s) -43.132 (-43d 07' 56")
   342.607 (22h 50m 26s) -49.680 (-49d 40' 48")
  ---------------------------------------------
The error box area is 1584 sq. arcmin, and its maximum
dimension is 6.8 deg (the minimum one is 4 arcmin).
The Sun distance was 95 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations (GCN Circ. 30071 and 30073).

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210524_T18010/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210524A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30077
SUBJECT: Konus-Wind detection of GRB 210524A
DATE:    21/05/25 16:04:23 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, S. Golenetskii, D. Frederiks, M. Ulanov,
A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 210524A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30071;
IPN triangulation: Hurley et al., GCN Circ. 30076)
triggered Konus-Wind at T0=18010.925 s UT (05:00:10.925).

The burst light curve shows a multi-peaked structure
which starts at ~T0-3.5 s and has a total duration of ~11.5 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210524_T18010/

As observed by Konus-Wind, the burst
had a fluence of 8.64(-0.52,+0.56)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+2.752 s,
of 3.76(-1.00,+1.00)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.33(-0.19,+0.20)
and Ep = 99(-10,+11) keV (chi2 = 45/56 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.7
(chi2 = 45/55 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.


GRB_name: GRB210524B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30078
SUBJECT: Fermi GRB 210524B: DDOTI Upper Limits on the Afterglow
DATE:    21/05/25 16:25:45 GMT
FROM:    Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada  <mpereyra@astro.unam.mx>

Margarita Pereyra (UNAM), Nat Butler (ASU), Alan M. Watson (UNAM), Eleonora
Troja (GSFC/UMD),  Simone Dichiara (GSFC/UMD), Rosa L. Becerra (UNAM),
William H. Lee (UNAM), OcÃ©lotl LÃ³pez,  Diego Gonzalez (UNAM), Alexander
Kutyrev (GSFC/UMD), and Srihari Ravi (ASU), report:

We observed the field of the likely long Fermi GRB 210524B  (trigger
643548039, GCN #30074, Fermi GBM Team) with the DDOTI/OAN wide-field imager
at the Observatorio AstronÃ³mico Nacional on Sierra San Pedro MÃ¡rtir (
http://ddoti.astroscu.unam.mx) on 2021-05-25 from 03:32:24 to 04:48:24 UTC
(16.19 to 17.46 hours  after the event).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA: 148.460
DEC: 7.79 (J2000 degrees). This region contains 6 instrumental fields or
about 400 square degrees. We obtained 600 to 720 seconds of exposure per
instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.

We detect no likely candidate for the afterglow to our 10-sigma upper
limits of w = 18.52 - 18.84 (inter-quartile).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30080
SUBJECT: GRB 210306A: LBT observations of the likely host galaxy
DATE:    21/05/26 12:33:42 GMT
FROM:    Andrea Rossi at INAF  <andrea.rossi@inaf.it>

A Rossi (INAF-OAS) and D. B. Malesani (DTU space) report on behalf of 
the CIBO collaboration:

We observed the field of GRB 210306A (D'Elia et al., GCN 29597) 
simultaneously in the r' and z' bands with the LBC imager mounted on LBT 
(Mt Graham, AZ, USA). We obtained 20min of imaging on 2021-05-10, 65 
days after the burst trigger and 60 days after our first observation 
(Rossi et al., GCN 29645). Observations were performed under good 
weather conditions with an average seeing of ~1.3".

At the location of the optical afterglow, we detected an object which is 
likely the GRB host galaxy. We measure the following AB magnitudes:

r=24.6+-0.2
z=24.4+-0.4

calibrated against SDSS field stars.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly A. Cardwell, S. Allanson, F. Cusano, S. Paiano and D. 
Paris, in obtaining these observations.


GRB_name: GRB210527A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30081
SUBJECT: GRB 210527A: Swift detection of a burst
DATE:    21/05/27 07:22:18 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

S. Laha (GSFC/UMBC/CRESST), P. A. Evans (U Leicester),
K. L. Page (U Leicester) and B. Sbarufatti (PSU) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 07:07:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210527A (trigger=1051453).  Swift did not slew immediately 
due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 172.355, +31.618 which is 
   RA(J2000) = 11h 29m 25s
   Dec(J2000) = +31d 37' 06"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is normal for an image trigger, the BAT 
light curve does not show any significant structure. 

Due to an observing constraint, Swift will not slew until T0+49.6
minutes. There will be no XRT or UVOT data until this time. 

Burst Advocate for this burst is S. Laha (sib.laha AT gmail.com). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210527A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30082
SUBJECT: GRB 210527A: Swift-XRT observations
DATE:    21/05/27 08:40:43 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), G.
Tagliaferri (INAF-OAB), S. Campana (INAF-OAB) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

The XRT began observing the field of GRB 210527A at 08:00:28.4 UT,
3159.5 seconds after the BAT trigger. Using promptly downlinked data we
find an uncatalogued X-ray source located at RA, Dec 172.32169,
31.62421 which is equivalent to:
   RA(J2000)  = 11h 29m 17.21s
   Dec(J2000) = +31d 37' 27.2"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 104 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper.  We cannot determine whether the source
is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.85
x 10^20 cm^-2 (Willingale et al. 2013). 


GRB_name: GRB210527A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30083
SUBJECT: GRB 210527A: Enhanced Swift-XRT position
DATE:    21/05/27 14:44:11 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1707 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 210527A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 172.32085, +31.62621 which is equivalent
to:

RA (J2000): 11h 29m 17.00s
Dec (J2000): +31d 37' 34.3"

with an uncertainty of 2.3 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210527A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30084
SUBJECT: GRB 210527A: RATIR Optical and NIR Observations
DATE:    21/05/27 17:53:44 GMT
FROM:    Nat Butler at Az State U  <natbutler@asu.edu>

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI), Eleonora
Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), JesÃºs
GonzÃ¡lez (UNAM), Carlos RomÃ¡n-ZÃºÃ±iga (UNAM), Harvey Moseley (GSFC), John
Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki Toy (UMD) report:

We observed the field of GRB 210527A (Laha, et al., GCN 30081) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold
Johnson Telescope at the Observatorio AstronÃ³mico Nacional on Sierra San
Pedro MÃ¡rtir from 2021/05 27.30 to 2021/05 27.32 UTC (0.01 to 0.56 hours
after the BAT trigger), obtaining a total of 0.19 hours exposure in the r
and i bands and 0.25 hours exposure in the Z, Y, J, and H bands.

We find no new sources within the refined XRT error region (Evans, et al.,
GCN 30083).   In comparison with the SDSS DR9 and 2MASS catalogs, we obtain
the following upper limits (3-sigma):

  r     > 21.67
  i     > 21.70
  Z     > 21.54
  Y     > 21.32
  J     > 20.78
  H     > 20.42

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210527A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30085
SUBJECT: GRB 210527A: Swift-XRT refined Analysis
DATE:    21/05/27 17:56:04 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU),
A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.
Melandri (INAF-OAB) and  report on behalf of the Swift-XRT team: report
on behalf of the Swift-XRT team:

We have analysed 7.1 ks of XRT data for GRB 210527A, from 3.2 ks to
27.7 ks after the  BAT trigger. The data are entirely in Photon
Counting (PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.90 (+0.23, -0.20).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.1 (+0.6, -0.5). The
best-fitting absorption column is  6.6 (+2.6, -2.1) x 10^21 cm^-2, in
excess of the Galactic value of 1.8 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 2.6 x 10^-11 (1.3 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.6 (+2.6, -2.1) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^20 cm^-2
Excess significance: 5.0 sigma
Photon index:      3.1 (+0.6, -0.5)

If the light curve continues to decay with a power-law decay index of
0.90, the count rate at T+24 hours will be 4.0 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-13 (5.1 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01051453.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210527A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30086
SUBJECT: Swift GRB 210527A: Global MASTER-Net observations report 
DATE:    21/05/27 18:53:22 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210527A ( S. Laha et al., GCN 30081) errorbox  41282 sec after notice time and 41473 sec after trigger time at 2021-05-27 18:39:02 UT, with upper limit up to  19.2 mag. The observations began at zenith distance = 30 deg. The sun  altitude  is -17.1 deg. 

The galactic latitude b = 72 deg., longitude l = 195 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1622598

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   41564 |   MASTER-Kislovodsk |   C |   180 | 18.5 |        
   41564 |   MASTER-Kislovodsk |   C |   180 | 19.2 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210527A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30087
SUBJECT: GRB 210527A: MITSuME Akeno optical upper limits
DATE:    21/05/28 05:47:33 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

Y. Imai, R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu,
S. Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210527A (S. Laha et al. GCN Circular
#30081, J.P. Osborne et al. GCN Circular #30082, P.A. Evans et al. GCN
Circular #30083, Nat Butler et al. GCN Circular #30084, V. D'Elia et
al. GCN Circular #30085, V. Lipunov et al. GCN Circular #30086) with
the optical three color (g', Rc, and Ic) CCD cameras attached to the
MITSuME 50 cm telescope Akeno.
The observation with a series of 60 sec exposures started at 2021-05-27
10:23:37 UT (3.3 hours after the triggers). We stacked the images with
good conditions. We did not detect any sources within the enhanced XRT
error region (P.A. Evans et al. GCN Circular #30083) in all three
bands. We obtained the 5-sigma limits of the stacked images as
follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
3.3 2021-05-27 15:28 1980 g'>18.0, Rc>18.6, Ic>18.1
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration. The magnitudes are
expressed in the AB system. The images were processed in real-time
through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ,
Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210527A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30088
SUBJECT: GRB 210527A: GIT optical upper limit
DATE:    21/05/28 07:33:04 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), U. Stanzin (IAO), G. C. Anupama(IIA), V. Bhalerao(IITB), S.
Barway(IIA) report on behalf of the GIT team:

We observed GRB 210527A detected by Swift-BAT (S. Laha et al., GCN #30081)
with the 0.7m GROWTH-India Telescope (GIT). We obtained 10 exposures, each
of 300 sec, in the r' filter starting at ~467 mins after the trigger. We
did not detect any new source in our stacked image within a 3 arcmin circle
around R.A. = 11h 29m 25s Dec(J2000) = +31d 37' 06" (GCN #30081). The
obtained upper limit follows as:

-------------------------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Exposure(sec) | Filter | Lim_mag (5-sigma) |

-------------------------------------------------------------------------

 2459362.1416 | ~8.27 | 3000 (stacked) | r' | > 21.98 |

-------------------------------------------------------------------------

Our upper limit is consistent with Nat Butler et al., GCN #30084; V.
Lipunov et al., GCN #30086; Y. Imai et al., GCN #30087. The magnitude is
calibrated against PanSTARRS (Flewelling et al., 2018) and not corrected
for Galactic extinction.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7 degree
field of view, set up by the Indian Institute of Astrophysics and the
Indian Institute of Technology Bombay with support from the Indo-US Science
and Technology Forum (IUSSTF) and the Science and Engineering Research
Board (SERB) of the Department of Science and Technology (DST), Government
of India (https://sites.google.com/view/growthindia/). It is located at the
Indian Astronomical Observatory (Hanle), operated by the Indian Institute
of Astrophysics (IIA).


GRB_name: GRB210527A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30089
SUBJECT: GRB 210527A: Swift/UVOT Observations
DATE:    21/05/28 12:22:26 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and S. L. Laha (GSFC/UMBC/CRESST)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210527A
3164 s after the BAT trigger (Laha et al., GCN Circ. 30081).
No optical afterglow consistent with the XRT position
(Evans et al., GCN Circ. 30083) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC          3164         3313          147         >20.2
white             3164         3932          344         >21.2
v                 4143         4343          197         >19.4
b                 3528         3727          197         >20.4
u                 3322         4895          331         >20.4
w1                4553         4753          197         >20.2
m2                4348         4548          197         >20.0
w2                3938         4138          197         >20.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.023 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210528A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30090
SUBJECT: GRB 210528A: Fermi GBM Final Real-time Localization
DATE:    21/05/28 14:14:06 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 14:03:46 UT on 28 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210528A (trigger 643903431.162588 / 210528586).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 134.1, Dec = -16.3 (J2000 degrees, equivalent to J2000 08h 56m, -16d 18'), with a statistical uncertainty of 1.9 degrees.

The angle from the Fermi LAT boresight is 55.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210528586/quicklook/glg_skymap_all_bn210528586.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210528586/quicklook/glg_healpix_all_bn210528586.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210528586/quicklook/glg_lc_medres34_bn210528586.gif


GRB_name: GRB210528A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30091
SUBJECT: GRB 210528A: BALROG localization (Fermi Trigger 643903431 / GRB 210528586)
DATE:    21/05/28 14:24:25 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
643903431 at 14:03:46 on 28 May 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 137.1+/-2.2 deg
Decl.(2000.0) = -14.0+/-2.4 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210528586/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210528586/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210528586/json

                        


GRB_name: GRB210527A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30092
SUBJECT: GRB 210527A: Swift-BAT refined analysis
DATE:    21/05/28 22:26:49 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210527A (trigger #1051453)
(Laha et al., GCN Circ. 30081).  The BAT ground-calculated position is
RA, Dec = 172.346, 31.627 deg which is
   RA(J2000)  =  11h 29m 23.0s
   Dec(J2000) = +31d 37' 37.0"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 90%.

The BAT light curve showed a complex structure with a duration of about ~70 sec.
T90 (15-350 keV) is 63.21 +- 11.15 sec (estimated error including systematics).

The time-averaged spectrum from T-17.07 to T+62.45 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.33 +- 0.26.  The fluence in the 15-150 keV band is 6.5 +- 1.0 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+17.86 sec in the 15-150 keV band
is 0.4 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1051453/BA/


GRB_name: GRB210528A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30093
SUBJECT: Fermi GRB 210528A: Global MASTER-Net observations report 
DATE:    21/05/28 23:15:13 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210528A ( Fermi GBM team, GCN 30090) errorbox  23846 sec after notice time and 23874 sec after trigger time at 2021-05-28 20:41:40 UT, with upper limit up to  18.1 mag. Observations started at twilight.  The observations began at zenith distance = 61 deg. The sun  altitude  is -10.4 deg. 

The galactic latitude b = 19 deg., longitude l = 244 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1623301

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   23904 | 2021-05-28 20:41:40 |          MASTER-IAC | (09h 02m 44.74s , -13d 49m 49.9s) |   C |    60 | 16.3 |        
   24064 | 2021-05-28 20:44:20 |          MASTER-IAC | (09h 07m 35.44s , -15d 45m 51.5s) |   C |    60 | 16.7 |        
   24224 | 2021-05-28 20:46:59 |          MASTER-IAC | (09h 00m 12.10s , -15d 50m 05.1s) |   C |    60 | 17.2 |        
   24224 | 2021-05-28 20:46:59 |          MASTER-IAC | (08h 51m 50.12s , -15d 44m 39.9s) |   C |    60 | 16.6 |        
   24463 | 2021-05-28 20:50:59 |          MASTER-IAC | (08h 55m 21.79s , -13d 57m 05.7s) |   C |    60 | 17.5 |        
   24463 | 2021-05-28 20:50:59 |          MASTER-IAC | (08h 47m 03.96s , -13d 51m 40.4s) |   C |    60 | 17.0 |        
   24623 | 2021-05-28 20:53:38 |          MASTER-IAC | (09h 05m 43.99s , -17d 44m 47.2s) |   C |    60 | 17.8 |        
   24623 | 2021-05-28 20:53:38 |          MASTER-IAC | (08h 57m 16.72s , -17d 39m 23.2s) |   C |    60 | 17.4 |        
   24863 | 2021-05-28 20:57:39 |          MASTER-IAC | (09h 02m 46.24s , -13d 50m 39.8s) |   C |    60 | 17.5 |        
   25423 | 2021-05-28 21:06:59 |          MASTER-IAC | (09h 07m 34.43s , -15d 44m 11.1s) |   C |    60 | 17.9 |        
   28711 | 2021-05-28 22:01:46 |          MASTER-IAC | (09h 00m 07.99s , -15d 52m 31.3s) |   C |    60 | 18.1 |        
   28950 | 2021-05-28 22:05:46 |          MASTER-IAC | (08h 55m 24.26s , -13d 58m 30.1s) |   C |    60 | 18.1 |        
   29110 | 2021-05-28 22:08:26 |          MASTER-IAC | (09h 05m 38.03s , -17d 45m 24.2s) |   C |    60 | 18.1 |        
   29670 | 2021-05-28 22:17:46 |          MASTER-IAC | (09h 00m 15.02s , -15d 50m 52.6s) |   C |    60 | 18.0 |        
   29910 | 2021-05-28 22:21:45 |          MASTER-IAC | (08h 55m 27.00s , -13d 57m 44.5s) |   C |    60 | 17.9 |        
   30070 | 2021-05-28 22:24:25 |          MASTER-IAC | (09h 05m 44.96s , -17d 46m 24.8s) |   C |    60 | 18.0 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210528B
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30094
SUBJECT: GRB 210528B: MAXI/GSC detection
DATE:    21/05/29 00:38:27 GMT
FROM:    Motoko Serino at Aoyama Gakuin U.  <serino@phys.aoyama.ac.jp>

Y. Sugawara (JAXA), H. Negoro, M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.),
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, M. Serino, S. Sugita, K. Komachi, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, M. Niwano, R. Hosokawa (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA),
Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.),
H. Tsunemi (Osaka U.),
M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU),
M. Sugizaki (NAOC) report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source 
at 22:51:37 UT on 2021 May 28.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (239.539 deg, 5.983 deg) = (15 58 09, +05 58 58) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.26 deg and 0.22 deg, respectively.
The roll angle of long axis from the north direction is 133.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(238.974, 6.826) deg = (15 55 53, +06 49 33) (J2000)
(238.661, 6.518) deg = (15 54 38, +06 31 04) (J2000)
(240.060, 5.113) deg = (16 00 14, +05 06 46) (J2000)
(240.373, 5.421) deg = (16 01 29, +05 25 15) (J2000)
The X-ray flux averaged over the scan was 170 +- 28 mCrab (4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at 21:18 UT
and in the next transit at 00:24 on May 29 UT with an upper limit of 20 mCrab for each.


GRB_name: GRB210528B
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30096
SUBJECT: GRB 210528B: MITSuME Akeno optical upper limits
DATE:    21/05/29 13:57:33 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

K. L. Murata, R. Hosokawa, M. Niwano, Y. Imai, N. Ito, H. Takamatsu, S.
Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 210528B (Sugawara et al. GCN Circular #30094,
Lipunov et al. GCN Circular #30095) with the optical three color (g', Rc,
and Ic) CCD cameras attached to the MITSuME telescope Akeno. The
observation with a series of 60 sec exposures started at 2021-05-29
11:21:57 UT (12.5 hours after the trigger). We stacked the images with good
conditions. We did not detect any uncatalogued sources in all three bands
within the elliptical error region (Sugawara et al. GCN Circular #30094)
determined under the assumption that the source flux was constant over the
transit. We obtained the 5-sigma limits of the stacked images as follows.

T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
12.5 2021-05-29 12:13 1560 g'>19.9
12.5 2021-05-29 12:13 2040 Rc>20.2
12.5 2021-05-29 12:13 1500 Ic>19.4
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the PS1 catalog for flux calibration. The magnitudes are expressed
in the AB system. The images were processed in real-time through the
MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1,
Pages 4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210528B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30097
SUBJECT: GRB 210528B: DDOTI Upper Limits on the Afterglow 
DATE:    21/05/29 14:32:38 GMT
FROM:    Alan M Watson at UNAM  <alan@astro.unam.mx>

Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara
(GSFC/UMD), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), OcÃ©lotl Lopez
(UNAM), Diego Gonzalez (UNAM), Margarita Pereyra (UNAM), Srihari Ravi (ASU), and
Eleonora Troja (GSFC/UMD) report:

We observed the field of the MAXI/GSC GRB 210528B (Sugawara et al., GCN Circ.,
30094) with the DDOTI wide-field imager at the Observatorio AstronÃ³mico Nacional
on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2021-05-29 04:07
to 06:53 UTC (from 5.3 to 8.0 hours after the trigger).

We observed a region covering aproximately 7 degrees in RA and 10 degrees in
declination (1 instrumental field or about 70 square degrees) including the
entire MAXI/GSC uncertainty region centered on 15:58:09 +05:58:58 J2000
(Sugawara et al., GCN Circ., 30094). We obtained 7860 seconds of exposure in the
w filter. We obtained AB photometry by calibration against the APASS catalog.

Within the uncertainty region, we detect no likely candidate for the afterglow
to our 5-sigma upper limits of w = 21.8.

We thank the staff of the Observatorio Astronomico Nacional in San Pedro Martir.


GRB_name: GRB210528A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30098
SUBJECT: GRB 210528A: AstroSat CZTI detection
DATE:    21/05/29 14:46:52 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a short GRB 210528A, which
was also detected by Fermi-GBM (GCN #30090).

The source was clearly detected in the 20 - 200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-05-28 14:03:45.5 UT. The measured peak count rate associated with
the burst is 682 (+186, -164) cts/s above the background in the combined
data of all four quadrants, with a total of 307 (+69, -65) cts. The
local mean background count rate was 547 (+9, -11) cts/s. Using
cumulative rates, we measure a T90 of 0.89 (+0.2, -0.3) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100 - 500 keV energy range. 

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC
and PRL. The Indian Space Research Organisation funded, managed and
facilitated the project. 

Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb


GRB_name: GRB210528A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30099
SUBJECT: GRB 210528A: Fermi GBM detection
DATE:    21/05/29 15:34:40 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P. Veres and C. Meegan (both UAH)
report on behalf of the Fermi GBM Team:

"At 14:03:46.16 UT on 28 May 2021, the Fermi Gamma-Ray Burst Monitor
(GBM) triggered and located GRB 210528A (trigger 643903431 /
210528586).

The on-ground calculated location, using the GBM trigger data, is
reported in GCN #30090.

The GBM light curve consists of a strong pulse with some overlapping
structure and a duration (T90) of about 1 s (50-300 keV). The
time-averaged spectrum from T0-0.3 s to T0+1.3 s is
best fit by a power law function with an exponential high-energy
cutoff.  The power law index is -0.47 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 210 +/- 9 keV.

The event fluence (10-1000 keV) in this time interval is (3.90 +/-
0.12)E-6 erg/cm^2. The 64ms peak photon flux measured starting from T0
+ 0.256 s in the 10-1000 keV band is 31.7 +/- 2.0 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210529A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30100
SUBJECT: GRB 210529A: Fermi GBM Final Real-time Localization
DATE:    21/05/29 16:25:42 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 16:15:24 UT on 29 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210529A (trigger 643997729.72023 / 210529677).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 15.8, Dec = -15.7 (J2000 degrees, equivalent to J2000 01h 03m, -15d 41'), with a statistical uncertainty of 10.9 degrees.

The angle from the Fermi LAT boresight is 69.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210529677/quicklook/glg_skymap_all_bn210529677.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210529677/quicklook/glg_healpix_all_bn210529677.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210529677/quicklook/glg_lc_medres34_bn210529677.gif


GRB_name: GRB210529B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30101
SUBJECT: GRB 210529B: Fermi GBM Final Real-time Localization
DATE:    21/05/30 00:04:01 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 23:53:37 UT on 29 May 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210529B (trigger 644025222.097546 / 210529996).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 230.0, Dec = 36.3 (J2000 degrees, equivalent to J2000 15h 20m, 36d 17'), with a statistical uncertainty of 5.8 degrees.

The angle from the Fermi LAT boresight is 16.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210529996/quicklook/glg_skymap_all_bn210529996.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210529996/quicklook/glg_healpix_all_bn210529996.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210529996/quicklook/glg_lc_medres34_bn210529996.gif


GRB_name: GRB210529B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30102
SUBJECT: Fermi GRB 210529B: Global MASTER-Net observations report 
DATE:    21/05/30 00:35:27 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210529B ( Fermi GBM team, GCN 30101) errorbox  252 sec after notice time and 280 sec after trigger time at 2021-05-29 23:58:17 UT, with upper limit up to  19.1 mag. The observations began at zenith distance =  8 deg. The sun  altitude  is -38.1 deg. 

The galactic latitude b = 57 deg., longitude l = 58 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1624282

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     310 | 2021-05-29 23:58:17 |          MASTER-IAC | (15h 17m 31.41s , +35d 28m 38.8s) |   C |    60 | 18.8 |        
     310 | 2021-05-29 23:58:17 |          MASTER-IAC | (15h 07m 30.80s , +35d 34m 29.3s) |   C |    60 | 18.6 |        
     391 | 2021-05-29 23:59:37 |          MASTER-IAC | (15h 21m 01.51s , +37d 22m 04.4s) |   C |    60 | 18.7 |        
     391 | 2021-05-29 23:59:37 |          MASTER-IAC | (15h 10m 46.10s , +37d 28m 00.1s) |   C |    60 | 18.4 |        
     471 | 2021-05-30 00:00:57 |          MASTER-IAC | (15h 33m 13.00s , +33d 34m 59.5s) |   C |    60 | 18.7 |        
     471 | 2021-05-30 00:00:57 |          MASTER-IAC | (15h 23m 25.79s , +33d 40m 54.3s) |   C |    60 | 18.6 |        
     551 | 2021-05-30 00:02:18 |          MASTER-IAC | (15h 15m 03.67s , +33d 34m 18.4s) |   C |    60 | 18.8 |        
     551 | 2021-05-30 00:02:18 |          MASTER-IAC | (15h 05m 16.33s , +33d 40m 11.9s) |   C |    60 | 18.8 |        
     661 | 2021-05-30 00:03:38 |          MASTER-IAC | (15h 19m 11.04s , +36d 24m 22.1s) |  P| |   120 | 18.7 |        
     661 | 2021-05-30 00:03:38 |          MASTER-IAC | (15h 18m 01.83s , +36d 31m 04.7s) |  P- |   120 | 18.4 |        
     816 | 2021-05-30 00:05:57 |          MASTER-IAC | (15h 19m 17.02s , +36d 24m 53.4s) |  P| |   150 | 18.8 |        
     816 | 2021-05-30 00:05:57 |          MASTER-IAC | (15h 18m 08.10s , +36d 31m 35.7s) |  P- |   150 | 18.5 |        
    1001 | 2021-05-30 00:08:47 |          MASTER-IAC | (15h 19m 13.77s , +36d 26m 07.6s) |  P| |   180 | 19.1 |        
    1001 | 2021-05-30 00:08:47 |          MASTER-IAC | (15h 18m 04.84s , +36d 32m 50.5s) |  P- |   180 | 18.7 |        
    1201 | 2021-05-30 00:12:07 |          MASTER-IAC | (15h 19m 13.75s , +36d 24m 33.0s) |  P| |   180 | 19.0 |        
    1201 | 2021-05-30 00:12:07 |          MASTER-IAC | (15h 18m 04.74s , +36d 31m 16.4s) |  P- |   180 | 18.7 |        
    1541 | 2021-05-30 00:18:48 |          MASTER-IAC | (15h 17m 24.50s , +35d 28m 03.3s) |   C |    60 | 18.8 |        
    1541 | 2021-05-30 00:18:48 |          MASTER-IAC | (15h 07m 21.55s , +35d 33m 50.6s) |   C |    60 | 18.6 |        
    1621 | 2021-05-30 00:20:08 |          MASTER-IAC | (15h 21m 02.63s , +37d 23m 00.6s) |   C |    60 | 18.6 |        
    1621 | 2021-05-30 00:20:08 |          MASTER-IAC | (15h 10m 44.61s , +37d 28m 50.2s) |   C |    60 | 18.4 |        
    1701 | 2021-05-30 00:21:28 |          MASTER-IAC | (15h 33m 19.34s , +33d 33m 54.7s) |   C |    60 | 18.7 |        
    1701 | 2021-05-30 00:21:28 |          MASTER-IAC | (15h 23m 29.92s , +33d 39m 42.6s) |   C |    60 | 18.6 |        
    1782 | 2021-05-30 00:22:48 |          MASTER-IAC | (15h 14m 57.26s , +33d 33m 11.5s) |   C |    60 | 18.8 |        
    1782 | 2021-05-30 00:22:48 |          MASTER-IAC | (15h 05m 07.82s , +33d 38m 59.1s) |   C |    60 | 18.8 |        
    1862 | 2021-05-30 00:24:08 |          MASTER-IAC | (15h 25m 57.96s , +39d 15m 20.3s) |   C |    60 | 18.7 |        
    1862 | 2021-05-30 00:24:08 |          MASTER-IAC | (15h 15m 24.33s , +39d 21m 08.8s) |   C |    60 | 18.5 |        
    1942 | 2021-05-30 00:25:29 |          MASTER-IAC | (15h 36m 07.87s , +35d 28m 48.9s) |   C |    60 | 18.8 |        
    1942 | 2021-05-30 00:25:29 |          MASTER-IAC | (15h 26m 05.43s , +35d 34m 35.4s) |   C |    60 | 18.5 |        
    2022 | 2021-05-30 00:26:49 |          MASTER-IAC | (15h 40m 11.85s , +37d 20m 49.6s) |   C |    60 | 18.7 |        
    2022 | 2021-05-30 00:26:49 |          MASTER-IAC | (15h 29m 54.85s , +37d 26m 36.9s) |   C |    60 | 18.5 |        
    2102 | 2021-05-30 00:28:09 |          MASTER-IAC | (15h 06m 20.21s , +39d 17m 14.5s) |   C |    60 | 18.6 |        
    2102 | 2021-05-30 00:28:09 |          MASTER-IAC | (14h 55m 46.53s , +39d 23m 01.4s) |   C |    60 | 18.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210529A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30103
SUBJECT: Fermi GRB 210529A: Global MASTER-Net observations report 
DATE:    21/05/30 07:45:09 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-IAC robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210529A ( Fermi GBM team, GCN 30100) errorbox  46458 sec after notice time and 46483 sec after trigger time at 2021-05-30 05:10:08 UT, with upper limit up to  16.7 mag. Observations started at twilight.  The observations began at zenith distance = 77 deg. The sun  altitude  is -11.8 deg. 

The galactic latitude b = -78 deg., longitude l = 140 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1624095

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   46514 | 2021-05-30 05:10:08 |          MASTER-IAC | (00h 57m 36.05s , -15d 53m 40.4s) |   C |    60 | 16.7 |        
   46594 | 2021-05-30 05:11:28 |          MASTER-IAC | (00h 57m 10.58s , -14d 00m 40.8s) |   C |    60 | 16.6 |        
   46674 | 2021-05-30 05:12:48 |          MASTER-IAC | (00h 58m 11.01s , -17d 49m 42.8s) |   C |    60 | 16.4 |        
   46754 | 2021-05-30 05:14:08 |          MASTER-IAC | (01h 04m 58.61s , -12d 12m 43.3s) |   C |    60 | 14.0 |        
   46754 | 2021-05-30 05:14:08 |          MASTER-IAC | (00h 56m 43.43s , -12d 07m 22.0s) |   C |    60 | 16.4 |        
   46836 | 2021-05-30 05:15:30 |          MASTER-IAC | (01h 12m 13.21s , -12d 05m 52.7s) |   C |    60 | 16.3 |        
   46916 | 2021-05-30 05:16:51 |          MASTER-IAC | (01h 04m 29.02s , -10d 18m 54.0s) |   C |    60 | 15.6 |        
   46916 | 2021-05-30 05:16:51 |          MASTER-IAC | (00h 56m 17.02s , -10d 13m 34.5s) |   C |    60 | 16.5 |        
   46998 | 2021-05-30 05:18:12 |          MASTER-IAC | (01h 12m 50.64s , -14d 00m 03.7s) |   C |    60 | 16.0 |        
   47078 | 2021-05-30 05:19:33 |          MASTER-IAC | (01h 13m 23.94s , -15d 54m 34.5s) |   C |    60 | 15.8 |        
   47159 | 2021-05-30 05:20:53 |          MASTER-IAC | (00h 58m 52.30s , -19d 41m 44.6s) |   C |    60 | 15.9 |        
   47239 | 2021-05-30 05:22:13 |          MASTER-IAC | (00h 50m 47.44s , -17d 54m 11.0s) |   C |    60 | 15.6 |        
   47239 | 2021-05-30 05:22:13 |          MASTER-IAC | (00h 42m 18.76s , -17d 48m 52.0s) |   C |    60 | 16.1 |        
   47319 | 2021-05-30 05:23:33 |          MASTER-IAC | (00h 49m 43.74s , -14d 07m 09.3s) |   C |    60 | 15.6 |        
   47319 | 2021-05-30 05:23:33 |          MASTER-IAC | (00h 41m 24.57s , -14d 01m 51.4s) |   C |    60 | 16.1 |        
   47497 | 2021-05-30 05:26:31 |          MASTER-IAC | (01h 06m 02.18s , -15d 59m 14.5s) |   C |    60 | 13.5 |        
   47497 | 2021-05-30 05:26:31 |          MASTER-IAC | (00h 57m 38.54s , -15d 53m 54.9s) |   C |    60 | 15.5 |        
   47577 | 2021-05-30 05:27:52 |          MASTER-IAC | (01h 05m 26.30s , -14d 06m 33.0s) |   C |    60 | 14.7 |        
   47577 | 2021-05-30 05:27:52 |          MASTER-IAC | (00h 57m 07.11s , -14d 01m 14.4s) |   C |    60 | 15.3 |        
   47657 | 2021-05-30 05:29:11 |          MASTER-IAC | (01h 06m 46.47s , -17d 53m 33.8s) |   C |    60 | 13.4 |        
   47657 | 2021-05-30 05:29:11 |          MASTER-IAC | (00h 58m 17.69s , -17d 48m 14.3s) |   C |    60 | 14.2 |        
   47738 | 2021-05-30 05:30:32 |          MASTER-IAC | (01h 04m 53.32s , -12d 12m 01.0s) |   C |    60 | 14.2 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210529B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30104
SUBJECT: GRB 210529B: DDOTI Upper Limits on the Afterglow
DATE:    21/05/31 02:02:56 GMT
FROM:    Kin O. C. L. Mendoza at Instituto de Astronoma, UNAM  <koclopez@astro.unam.mx>

OcÃ©lotl Lopez (UNAM), Margarita Pereyra (UNAM), Rosa L. Becerra (UNAM), Nat
Butler (ASU), Alan M. Watson (UNAM), Simone Dichiara (GSFC/UMD), Alexander
Kutyrev (GSFC/UMD), William H. Lee (UNAM), Diego Gonzalez (UNAM), Margarita
Pereyra (UNAM), Srihari Ravi (ASU), and Eleonora Troja (GSFC/UMD) report:

We observed the field of the Fermi GBM GRB 210529B (Fermi Collaboration,
GCN Circ. 30101) with the DDOTI wide-field imager at the Observatorio
AstronÃ³mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-05-30 03:35 to 11:19 UTC (3.7 to
11.4 hours after the trigger).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA: 230.01,
DEC: +36.34 (J2000 degrees). This region contains 6 instrumental fields or
about 400 square degrees. We obtained 58 minutes of exposure per
instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.

We detect no likely candidates for the afterglow to our 10-sigma upper
limits of w = 20.25-20.58 (inter-quartile).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
Martir.


GRB_name: GRB210531A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30105
SUBJECT: GRB 210531A: BALROG localization (Fermi Trigger 644155206 / GRB 210531500)
DATE:    21/05/31 12:24:39 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
644155206 at 12:00:01 on 31 May 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 140.9+/-0.5 deg
Decl.(2000.0) = 6.1+/-0.7 deg
We estimate an additional systematic error of 2 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210531500/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210531500/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210531500/json

                        


GRB_name: GRB210531A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30106
SUBJECT: GRB 210531A: AGILE/MCAL detection (Fermi Trigger 644155206 / GRB 210531500)
DATE:    21/05/31 14:19:02 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), F. Longo (Univ. Trieste and INFN Trieste), M. Tavani
(INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli, C. Pittori,
F. Verrecchia (SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano,  V.
Fioretti, F. Fuschino, N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi
(INAF/OAS-Bologna, and Bergen University), M. Pilia, A. Trois
(INAF/OA-Cagliari), I. Donnarumma (ASI), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:

The AGILE satellite detected the long GRB 210531A at T0 = 2021-05-31
12:00:02.66 +/- 0.01 s (UTC), reported by Fermi/GBM (Trigger no. 644155206)
and BALROG (GCN #30105).

The burst is clearly visible in the AGILE scientific ratemeters of the
SuperAGILE (SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and
AntiCoincidence (AC; 50-200 keV) detectors. The event lasted about 35 s and
it released a total number of 9650 counts in the SA detector (above a
background rate of 90 Hz), 53900 counts in the MCAL detector (above a
background rate of 1400 Hz), and 151900 counts in the AC detector (above a
background rate of 3780 Hz). The AGILE ratemeter light curves can be found
at http://www.agilescienceapp.it/notices/GRB210531A_AGILE_RM.png .

The event also triggered a partial high time resolution MCAL data
acquisition.

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.


GRB_name: GRB210531A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30108
SUBJECT: GRB 210531A: AstroSat CZTI detection
DATE:    21/06/01 06:59:20 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a long GRB 210531A, which
was also detected by AGILE/MCAL (GCN #30106) and Fermi (GCN #30105).

The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-05-31 12:00:04.5 UT. The measured peak count rate associated with
the burst is 1948 (+77, -87) cts/s above the background in the combined
data of four quadrants, with a total of 13005 (+281, -332) cts. The
local mean background count rate was 532 (+3.0, -2.9) cts/s. Using
cumulative rates, we measure a T90 of 20 (+0.2, -0.2)s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2021-05-31 12:00:04.9 UT. The
measured peak count rate is 2541 (+104, -114) cts/s above the background
in the combined Veto data of four quadrants, with a total of 16360
(+452, -552) cts. The local mean background count rate was 1729 (+5, -5)
cts/s. We measure a T90 of 19 (+1, -2) s from the cumulative Veto light
curve.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC
and PRL. The Indian Space Research Organisation funded, managed and
facilitated the project. 

Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb


GRB_name: GRB210529B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30109
SUBJECT: GRB210529B: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 644025222)
DATE:    21/06/01 10:04:08 GMT
FROM:    Tomas Ahumada at U. of Maryland  <tahumada@astro.umd.edu>

Tomas Ahumada (UMD), Shreya Anand (Caltech), Harsh Kumar (IIT-B), Igor
Andreoni (Caltech), Albert Kong (NTHU), Erik Kool (SU), Ana
Sagues-Carracedo (SU), Simeon Reusch (DESY), , Michael Coughlin (UMN),
Mansi Kasliwal (Caltech), Robert Stein (DESY), Leo Singer (NASA/GSFC), and
Matthew Graham (Caltech) report on behalf of the ZTF collaboration:

We observed the localization region of the short GRB210529B (trigger
644025222.097546) detected by the Gamma-Ray Burst Monitor (GBM) on the
Fermi satellite with the Palomar 48 inch telescope equipped with the 47
square degree Zwicky Transient Facility (ZTF; Bellm et al., 2019; Graham et
al., 2019) camera. We obtained a series of g- and r-band images covering
about 686 square degrees beginning at 05:06:36.18 UT on 2021-05-30 (~ 5.1
hours after the burst trigger time). This corresponds to ~85% of the
probability enclosed in the region of the GRB localization that was
unocculted by the Earth for Fermi GBM (GCN 30101). Exposures reached a
median depth of 22.2 mag in the g-band and 22.3 mag in the r-band.
On 2021-05-31, we obtained another epoch of g- and r-band follow-up
observations, beginning at 05:07:50.96 UT with exposures reaching a median
depth of 22.2 mag and 22.2 mag respectively, and covering ~85% of the
enclosed probability.

The images were processed in real-time through the ZTF reduction and image
subtraction pipelines at IPAC (Masci et al. 2019). We queried the ZTF alert
stream using Kowalski (Duev et al. 2019). We required at least 2 detections
separated by at least 15 minutes to select against moving objects.
Furthermore, we cross-matched our candidates with the Minor Planet Center
to flag known asteroids, reject stellar sources (Tachibana and Miller
2018), and apply machine learning algorithms (Duev et al. 2019, Mahabal et
al. 2019). We require no spatially coincident ZTF alert to be issued before
the detection time of the GBM trigger.

We identified 146 transient candidates located within the 95% probability
contour of the skymap that passed automatic selection criteria. The
majority of the transients showed no evolution between the two nights. We
performed forced photometry (Masci et al. 2019) on the candidates reported
below and found no previous history of variability.

+--------------+-----------+-------------+--------------+--------+-------+-----------+
|     Name     |  IAU Name |      RA     |     Dec      | disc. mag |
 notes     |
+--------------+-----------+-------------+--------------+--------+-------+-----------+
| ZTF21abcwmzx | AT2021nzo | 14:42:28.10 | +31:56:34.19 | g = 21.51 |
(1)(e)  |
| ZTF21abcwnbm | AT2021nzp | 14:43:43.24 | +33:44:52.20 | g = 21.54 |
(1)(d)  |
| ZTF21abcwuxv | AT2021nzq | 15:30:34.50 | +43:05:52.27 | r = 21.82 |
(a)(b) |
| ZTF21abcwvzr | AT2021nzr | 14:49:49.23 | +35:05:43.32 | r = 21.9  |
(a)(e) |
| ZTF21abcwwaj | AT2021nzs | 14:40:59.49 | +32:07:24.64 | r = 21.24 |
(a)(c) |
| ZTF21abcwyoe | AT2021nzt | 15:58:56.54 | +33:08:01.79 | r = 21.83 |
(a)(d) |
| ZTF21abcwyvi | AT2021nzu | 15:58:53.27 | +33:39:12.74 | r = 21.98 |
(a)(b) |

Notes:
(1) shows rise and rapid decay
(a) Non-detection during the second night (2021-05-31). These have two or
more detections separated by >50 min during the first night.
(b) hostless
(c) host at z=0.1
(d) nuclear
(e) likely offset from host

Based on observations obtained with the Samuel Oschin Telescope 48-inch and
the 60-inch Telescope at the Palomar Observatory as part of the Zwicky
Transient Facility project. ZTF is supported by the National Science
Foundation under Grant No. AST-2034437 and a collaboration including
Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center
at Stockholm University, the University of Maryland, Deutsches
Elektronen-Synchrotron and Humboldt University, the TANGO Consortium of
Taiwan, the University of Wisconsin at Milwaukee, Trinity College Dublin,
Lawrence Livermore National Laboratories, and IN2P3, France. Operations are
conducted by COO, IPAC, and UW.


-- 
Tomas Ahumada (he/him)
Ph.D. Candidate
Department of Astronomy
University of Maryland, College Park
NASA Goddard Space Flight Center, Code 661
B.Sc. Astronomy, Pontificia Universidad CatÃ³lica de Chile


GRB_name: GRB210531A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30110
SUBJECT: IPN triangulation of GRB 210531A
DATE:    21/06/01 17:29:39 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
report:

The bright, long-duration GRB 210531A
(BALROG localization: Biltzinger et al., GCN Circ. 30105;
AGILE detection: Ursi et al., GCN Circ. 30106;
AstroSat-CZTI detection: Sawant et al., GCN Circ. 30108)
was detected by Fermi (GBM trigger 644155206), Konus-Wind,
INTEGRAL (SPI-ACS), AGILE (MCAL, SA, and AC),
and AstroSat (CZTI) at about 43201 s UT (12:00:01).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   140.592 (09h 22m 22s)  +8.281 ( +8d 16' 50")
  Corners:
   141.277 (09h 25m 06s) +11.425 (+11d 25' 30")
   142.066 (09h 28m 16s) +10.564 (+10d 33' 51")
   139.800 (09h 19m 12s)  +5.254 ( +5d 15' 16")
   139.052 (09h 16m 12s)  +6.081 ( +6d 04' 51")
  ---------------------------------------------
The error box area is 5.9 sq. deg, and its maximum
dimension is 6.3 deg (the minimum one is 1 deg).
The Sun distance was 70 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi final position and BALROG (GCN Circ. 30105) localizations.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210531_T43198/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210601A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30111
SUBJECT: GRB 210601A: Fermi GBM Final Real-time Localization
DATE:    21/06/01 17:32:24 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 17:22:13 UT on 1 Jun 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210601A (trigger 644260938.537058 / 210601724).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 277.1, Dec = -26.7 (J2000 degrees, equivalent to J2000 18h 28m, -26d 41'), with a statistical uncertainty of 28.7 degrees.

The angle from the Fermi LAT boresight is 133.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210601724/quicklook/glg_skymap_all_bn210601724.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210601724/quicklook/glg_healpix_all_bn210601724.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210601724/quicklook/glg_lc_medres34_bn210601724.gif


GRB_name: GRB210601A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30112
SUBJECT: Fermi GRB 210601A: Global MASTER-Net observations report 
DATE:    21/06/02 02:32:35 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210601A ( Fermi GBM team, GCN 30111) errorbox  17545 sec after notice time and 17557 sec after trigger time at 2021-06-01 22:14:50 UT, with upper limit up to  17.4 mag. The observations began at zenith distance = 53 deg. The sun  altitude  is -23.1 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) started inspect of the Fermi GRB 210601A errorbox  25066 sec after notice time and 25077 sec after trigger time at 2021-06-02 00:20:11 UT, with upper limit up to  19.0 mag. The observations began at zenith distance = 57 deg. The sun  altitude  is -38.9 deg. 

The galactic latitude b = -8 deg., longitude l =  7 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1626114

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   17647 | 2021-06-01 22:14:50 |   MASTER-Kislovodsk | (19h 02m 09.26s , -07d 18m 48.6s) |   C |   180 | 16.9 |        
   17647 | 2021-06-01 22:14:50 |   MASTER-Kislovodsk | (19h 06m 27.80s , -07d 43m 31.9s) |   C |   180 | 17.2 |        
   17847 | 2021-06-01 22:18:11 |   MASTER-Kislovodsk | (19h 02m 43.26s , -05d 50m 39.1s) |   C |   180 | 17.1 |        
   17848 | 2021-06-01 22:18:11 |   MASTER-Kislovodsk | (19h 07m 01.71s , -06d 15m 20.8s) |   C |   180 | 17.4 |        
   18048 | 2021-06-01 22:21:31 |   MASTER-Kislovodsk | (19h 02m 12.53s , -07d 18m 39.2s) |   C |   180 | 16.6 |        
   18048 | 2021-06-01 22:21:31 |   MASTER-Kislovodsk | (19h 06m 31.53s , -07d 43m 23.3s) |   C |   180 | 16.9 |        
   18249 | 2021-06-01 22:24:52 |   MASTER-Kislovodsk | (19h 02m 40.58s , -05d 50m 08.7s) |   C |   180 | 17.1 |        
   18249 | 2021-06-01 22:24:52 |   MASTER-Kislovodsk | (19h 06m 59.31s , -06d 14m 49.8s) |   C |   180 | 17.3 |        
   18449 | 2021-06-01 22:28:12 |   MASTER-Kislovodsk | (19h 02m 06.55s , -07d 18m 28.5s) |   C |   180 | 16.6 |        
   18449 | 2021-06-01 22:28:12 |   MASTER-Kislovodsk | (19h 06m 25.83s , -07d 43m 11.9s) |   C |   180 | 16.8 |        
   18649 | 2021-06-01 22:31:32 |   MASTER-Kislovodsk | (19h 02m 47.47s , -05d 50m 04.4s) |   C |   180 | 15.7 |        
   18649 | 2021-06-01 22:31:32 |   MASTER-Kislovodsk | (19h 07m 06.66s , -06d 14m 43.8s) |   C |   180 | 16.1 |        
   25168 | 2021-06-02 00:20:11 |          MASTER-IAC | (19h 05m 57.87s , -07d 29m 43.1s) |   C |   180 | 17.2 |        
   25168 | 2021-06-02 00:20:11 |          MASTER-IAC | (18h 57m 48.97s , -07d 23m 54.5s) |   C |   180 | 17.1 |        
   25583 | 2021-06-02 00:27:06 |          MASTER-IAC | (19h 05m 57.28s , -07d 31m 47.0s) |   C |   180 | 17.2 |        
   25583 | 2021-06-02 00:27:06 |          MASTER-IAC | (18h 57m 48.34s , -07d 25m 59.1s) |   C |   180 | 17.1 |        
   25984 | 2021-06-02 00:33:47 |          MASTER-IAC | (19h 06m 01.32s , -07d 30m 03.4s) |   C |   180 | 17.2 |        
   25984 | 2021-06-02 00:33:47 |          MASTER-IAC | (18h 57m 52.02s , -07d 24m 16.0s) |   C |   180 | 17.4 |        
   27984 | 2021-06-02 01:07:07 |          MASTER-IAC | (19h 06m 38.06s , -06d 00m 46.2s) |   C |   180 | 17.4 |        
   27984 | 2021-06-02 01:07:07 |          MASTER-IAC | (18h 58m 29.15s , -05d 55m 05.1s) |   C |   180 | 17.4 |        
   28388 | 2021-06-02 01:13:51 |          MASTER-IAC | (19h 06m 33.12s , -06d 00m 20.4s) |   C |   180 | 17.5 |        
   28388 | 2021-06-02 01:13:51 |          MASTER-IAC | (18h 58m 24.56s , -05d 54m 37.4s) |   C |   180 | 17.4 |        
   28588 | 2021-06-02 01:17:11 |          MASTER-IAC | (19h 35m 20.14s , -07d 38m 19.1s) |   C |   180 | 18.3 |        
   28588 | 2021-06-02 01:17:11 |          MASTER-IAC | (19h 34m 30.41s , -07d 32m 50.5s) |   C |   180 | 18.5 |        
   28789 | 2021-06-02 01:20:32 |          MASTER-IAC | (19h 35m 12.98s , -07d 39m 21.4s) |   C |   180 | 18.3 |        
   28789 | 2021-06-02 01:20:32 |          MASTER-IAC | (19h 34m 23.45s , -07d 33m 52.2s) |   C |   180 | 18.6 |        
   28989 | 2021-06-02 01:23:52 |          MASTER-IAC | (19h 35m 20.18s , -07d 39m 20.7s) |   C |   180 | 18.3 |        
   28989 | 2021-06-02 01:23:52 |          MASTER-IAC | (19h 34m 30.83s , -07d 33m 50.7s) |   C |   180 | 18.7 |        
   29271 | 2021-06-02 01:28:34 |          MASTER-IAC | (19h 35m 13.32s , -07d 37m 34.4s) |   C |   180 | 18.9 |        
   29271 | 2021-06-02 01:28:34 |          MASTER-IAC | (19h 34m 23.81s , -07d 31m 41.9s) |   C |   180 | 18.7 |        
   29471 | 2021-06-02 01:31:54 |          MASTER-IAC | (19h 35m 13.40s , -07d 39m 08.1s) |   C |   180 | 18.9 |        
   29471 | 2021-06-02 01:31:54 |          MASTER-IAC | (19h 34m 23.87s , -07d 33m 14.0s) |   C |   180 | 18.6 |        
   29671 | 2021-06-02 01:35:14 |          MASTER-IAC | (19h 35m 17.00s , -07d 37m 47.7s) |   C |   180 | 19.0 |        
   29671 | 2021-06-02 01:35:14 |          MASTER-IAC | (19h 34m 27.59s , -07d 31m 53.5s) |   C |   180 | 18.7 |        
   30072 | 2021-06-02 01:41:55 |          MASTER-IAC | (19h 06m 33.09s , -06d 00m 31.6s) |   C |   180 | 18.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210602A
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30113
SUBJECT: GRB 210602A: MAXI/GSC detection
DATE:    21/06/02 12:44:38 GMT
FROM:    Motoko Serino at Aoyama Gakuin U.  <serino@phys.aoyama.ac.jp>

M. Serino, S. Sugita (AGU),
H. Negoro, M. Nakajima, K. Kobayashi, K. Asakura, K. Seino (Nihon U.),
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, K. Komachi, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, M. Niwano, R. Hosokawa (Tokyo Tech),
S. Nakahira, Y. Sugawara, S. Ueno, H. Tomida, M. Ishikawa, M. Tominaga, T. Nagatsuka (JAXA),
Y. Ueda, S. Yamada, S. Ogawa, K. Setoguchi, T. Yoshitake, Y. Goto, R. Uematsu (Kyoto U.),
H. Tsunemi (Osaka U.),
M. Yamauchi, Y. Nonaka, T. Sato, R. Hatsuda, R. Fukuoka (Miyazaki U.), T. Kawamuro (UDP/NAOJ),
K. Yamaoka (Nagoya U.),
Y. Kawakubo (LSU),
M. Sugizaki (NAOC) 
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued 
X-ray transient source at 12:04:02 UT on 2021 June 2.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (44.630 deg, -2.672 deg) = (02 58 31, -02 40 19) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.17 deg and 0.16 deg, respectively.
The roll angle of long axis from the north direction is 107.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 393 +- 52 mCrab
(4.0-10.0keV, 1 sigma error).
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (43.754, -3.549) deg = (02 55 00, -03 32 56) (J2000)
(R.A., Dec) = (44.013, -3.735) deg = (02 56 03, -03 44 05) (J2000)
(R.A., Dec) = (45.446, -1.751) deg = (03 01 47, -01 45 03) (J2000)
(R.A., Dec) = (45.187, -1.565) deg = (03 00 44, -01 33 53) (J2000)
There was no significant excess flux in the previous transit at 10:31 UT
with an upper limit of 20 mCrab.


GRB_name: GRB210529A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30115
SUBJECT: GRB 210529A: GECAM detection
DATE:    21/06/03 01:08:14 GMT
FROM:    QiBin Yi at IHEP, HXMT  <yiqb@ihep.ac.cn>

Q. B. Yi, S. Xiao, S. L. Xiong, X. Y. Zhao, X. Y. Song, Y. Huang,
C. Cai, Y. Zhao, C. Y. Li, J. C. Liu, Y. Q. Zhang, W. C. Xue, C. Zheng,
Z. W. Guo, X. L. Zhao, B. X. Zhang, C. W. Wang, S. L. Xie,
P. Wang, X. B. Li, W. X. Peng, R. Qiao, J. Wang, H. S. Zhao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long hard GRB,
GRB 210529A, at 2021-05-29T16:15:24.950 UTC (denoted as T0), 
which was also observed by Fermi/GBM (GCN #30100).

According to the GECAM-B light curves in about 8 keV-4 MeV, 
this burst mainly consists of multiple pulses with a duration of about 1.3s.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/multiLCvsE_tn210529_161524.png

GECAM-B localized this burst to the following position (J2000):
Ra: 40.4 deg
Dec: -12.9 deg
Err: 26.7 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. This position is 
consistent with the Fermi GBM team localization (GCN 30100) within the error.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210602B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30116
SUBJECT: GRB 210602B: GECAM detection
DATE:    21/06/03 06:11:28 GMT
FROM:    Yue Huang at IHEP  <huangyue@ihep.ac.cn>

X. Y. Zhao, S. L. Xiong, Y. Huang, S. Xiao, Y. Q. Du, J. Liang, Q. B. Yi,
X. Y. Song, D. Y. Guo, C. Cai, Y. Zhao, J. C. Liu, Y. Q. Zhang, W. C. Xue,   
Z. W. Guo, P. Wang, X. B. Li, W. X. Peng, R. Qiao, C. Zheng, C. W. Wang,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, C. Y. Li, J. H. Li, Q. X. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou,  D. L. Shi, J. Y. Shi, L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo,
J. Z. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, B. X. Zhang,
C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, GECAM-B triggered a long GRB 210602B
at 2021-06-02T20:46:04.400 UTC (denoted as T0), 
which was also observed by Fermi/GBM(trigger No 644359567).

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of 
multiple pulses with a duration of about 10s.  

An automatic on-ground localization was calculated using the light curves
and spectrum. Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
ra: 191.98 deg
dec: -54.42 deg
err: 24.48 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

GECAM location is consistent with the Fermi/GBM(trigger No 644359567) 
position within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_h3grd_76365964.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210602A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30117
SUBJECT: GRB 210602A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/06/03 07:04:45 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

V. Pal'shin, A. Yoshida, T. Sakamoto, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The bright GRB 210602A (MAXI/GSC detection: Serino et al., GCN Circ. 30113)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 12:04:01.493 UTC
on 2 June 2021
(http://cgbm.calet.jp/cgbm_trigger/flight/1306670489/index.html).
The burst signal was seen by all CGBM detectors.

The burst light curve shows a single pulse which starts at T+0.5 sec,
peaks at T+1.4 sec, and ends at T+3.0 sec. The T90 and T50 durations
measured by the SGM data are 1.9 +- 0.3 sec and 0.5 +- 0.1 sec (40-1000
keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1306670489/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210605A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30127
SUBJECT: GRB 210605A: Fermi GBM Final Real-time Localization
DATE:    21/06/05 05:19:24 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely SHORT GRB

At 05:08:58 UT on 5 Jun 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210605A (trigger 644562543.389178 / 210605215).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 21.7, Dec = -41.5 (J2000 degrees, equivalent to J2000 01h 26m, -41d 30'), with a statistical uncertainty of 2.0 degrees.

The angle from the Fermi LAT boresight is 128.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605215/quicklook/glg_skymap_all_bn210605215.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605215/quicklook/glg_healpix_all_bn210605215.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605215/quicklook/glg_lc_medres34_bn210605215.gif


GRB_name: GRB210605A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30128
SUBJECT: Fermi GRB 210605A: Global MASTER-Net observations report 
DATE:    21/06/05 05:32:21 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210605A ( Fermi GBM team, GCN 30127) errorbox  571 sec after notice time and 600 sec after trigger time at 2021-06-05 05:18:58 UT, with upper limit up to  17.2 mag. The observations began at zenith distance = 86 deg. The sun  altitude  is -76.8 deg. 

The galactic latitude b = -74 deg., longitude l = 277 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1628580

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     661 | 2021-06-05 05:18:58 |         MASTER-OAFA | (01h 24m 45.07s , -42d 19m 00.9s) |   C |   120 | 17.0 |        
    1023 | 2021-06-05 05:24:31 |         MASTER-OAFA | (01h 24m 38.95s , -42d 20m 23.9s) |   C |   180 | 17.3 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210605B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30129
SUBJECT: GRB 210605B: Fermi GBM Final Real-time Localization
DATE:    21/06/05 15:06:08 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 14:55:58 UT on 5 Jun 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210605B (trigger 644597763.075646 / 210605622).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 15.1, Dec = -6.5 (J2000 degrees, equivalent to J2000 01h 00m, -6d 30'), with a statistical uncertainty of 3.8 degrees.

The angle from the Fermi LAT boresight is 18.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605622/quicklook/glg_skymap_all_bn210605622.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605622/quicklook/glg_healpix_all_bn210605622.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210605622/quicklook/glg_lc_medres34_bn210605622.gif


GRB_name: GRB210605B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30130
SUBJECT: GRB 210605B: Swift/BAT-GUANO detection and arcminute localization
DATE:    21/06/06 00:21:21 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea
(PSU), Gayathri Raman (PSU) report:

Swift/BAT did not trigger on GRB 210605B (T0: 2021-06-06 14:55:58 UTC,
Fermi/GBM GCN 31029).

The Fermi/GBM notice, distributed in near real-time, triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is detected in BAT with a duration of at least 20 seconds.
The burst occurred during a Swift slew.
The position of the burst was found with SNR of 8.4 using a novel slew
image mosaicing procedure (DeLaunay et al. 2021, in prep.), and so the
positional uncertainty is not yet well characterized.

The BAT position is
RA, Dec = 15.732, -6.467 deg which is
   RA(J2000)  = 01h 02m 55.68s
   Dec(J2000) =  -6d 28â€² 1.2â€³
with an estimated uncertainty of 5 arcmin.

This position is consistent with the Ferm/GBM localization (GCN 31029).

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/


GRB_name: GRB210606A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30131
SUBJECT: GRB 210606A: Fermi GBM Final Real-time Localization
DATE:    21/06/06 04:06:18 GMT
FROM:    Fermi GBM Team at MSFC/Fermi-GBM  <do_not_reply@GIOC.nsstc.nasa.gov>

The Fermi GBM team reports the detection of a likely LONG GRB

At 03:56:02 UT on 6 Jun 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210606A (trigger 644644567.122922 / 210606164).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 177.6, Dec = -0.5 (J2000 degrees, equivalent to J2000 11h 50m, 0d 30'), with a statistical uncertainty of 11.4 degrees.

The angle from the Fermi LAT boresight is 110.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210606164/quicklook/glg_skymap_all_bn210606164.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210606164/quicklook/glg_healpix_all_bn210606164.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210606164/quicklook/glg_lc_medres34_bn210606164.gif


GRB_name: GRB210606A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30132
SUBJECT: Fermi GRB 210606A: Global MASTER-Net observations report 
DATE:    21/06/06 05:02:24 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-OAFA robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 210606A ( Fermi GBM team, GCN 30131) errorbox  707 sec after notice time and 735 sec after trigger time at 2021-06-06 04:08:17 UT, with upper limit up to  17.4 mag. The observations began at zenith distance = 74 deg. The sun  altitude  is -79.9 deg. 

The galactic latitude b = 59 deg., longitude l = 274 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1629491

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

     765 | 2021-06-06 04:08:17 |         MASTER-OAFA | (11h 48m 10.39s , +00d 06m 01.9s) |   C |    60 | 16.3 |        
    1046 | 2021-06-06 04:12:58 |         MASTER-OAFA | (11h 56m 10.96s , +00d 05m 07.4s) |   C |    60 | 17.1 |        
    1206 | 2021-06-06 04:15:38 |         MASTER-OAFA | (11h 56m 17.42s , +02d 00m 54.3s) |   C |    60 | 15.7 |        
    1286 | 2021-06-06 04:16:57 |         MASTER-OAFA | (11h 48m 44.03s , -01d 47m 01.2s) |   C |    60 | 17.0 |        
    1365 | 2021-06-06 04:18:17 |         MASTER-OAFA | (11h 56m 52.70s , -01d 47m 56.7s) |   C |    60 | 17.4 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210605B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30133
SUBJECT: GRB 210605B: Swift ToO observations
DATE:    21/06/06 11:33:22 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 210605B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021450

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210606A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30134
SUBJECT: GRB 210606A: Swift/BAT-GUANO detection and arcminute localization
DATE:    21/06/06 17:43:04 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

James DeLaunay (PSU), Aaron Tohuvavohu (U Toronto), Jamie A. Kennea
(PSU), Gayathri Raman (PSU) report:

Swift/BAT did not trigger on GRB 210606A (T0: 2021-06-06 03:56:02 UTC,
Fermi/GBM GCN 30131).  

The Fermi/GBM notice, distributed in near real-time, triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).

Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.

The burst is detected in BAT with a duration of ~8 seconds.
With a maximum likelihood analysis (DeLaunay et al. 2021, in prep.) on
the event-mode data we detect a location for the burst with a square
root of the test statistic, sqrt(TS), of 15. The sqrt(TS) behaves
similarly to SNR.
Using the normal BAT imaging technique, we find the same location for
the GRB with an SNR of 5.2.

The BAT position is
RA, Dec = 170.904,  +0.718 deg which is
   RA(J2000)  = 11h 23m 36.96s
   Dec(J2000) =  00d 43â€² 04.8â€³
with an estimated uncertainty of 4 arcmin.
The partial coding was 8%.

This position is consistent with the Ferm/GBM localization (GCN 30131).

XRT and UVOT follow-up has been requested. Results of follow-up
observations will be reported in future circulars.

GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.

A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/

[GCN OPS NOTE(06Jun21): Per author's request, the two places that cited
GCN 31031 have been changed to GCN 30131.]


GRB_name: GRB210606A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30135
SUBJECT: Fermi GRB 210606A: DDOTI Upper Limits on the Afterglow
DATE:    21/06/06 19:29:35 GMT
FROM:    Emma Margarita Pereyra Talamantes at IA-UNAM Ensenada  <mpereyra@astro.unam.mx>

Margarita Pereyra (UNAM), Alan M. Watson (UNAM), Nat Butler (ASU), Camila
Angulo,  Simone Dichiara (GSFC/UMD), Rosa L. Becerra (UNAM), William H. Lee
(UNAM), OcÃ©lotl LÃ³pez,  Eleonora Troja (GSFC/UMD), Diego Gonzalez (UNAM),
Alexander Kutyrev (GSFC/UMD), and Srihari Ravi (ASU), report:

We observed the field of the likely Long Fermi GRB 210606A  (trigger
644644567, GCN #30131, Fermi GBM Team) with the DDOTI/OAN wide-field imager
at the Observatorio AstronÃ³mico Nacional on Sierra San Pedro MÃ¡rtir (
http://ddoti.astroscu.unam.mx) on 2021/06/06 from 04:12:31.000 to
06:46:24.000 UTC (0.27 to 2.83 hours after the event).

We observed a region of 20.4 degrees in RA by 20.4 degrees in declination,
with a 3 x 2 grid, centered on the Fermi GBM Final Position RA: 177.630000,
DEC: -0.470000 (J2000 degrees). This region contains 6 instrumental fields
or about 400 square degrees. We obtained 1075 to 1200 seconds of exposure
per instrumental field in the w filter. We obtained AB photometry by
calibration against the APASS catalog.

We detect no likely candidates for the afterglow to our 10-sigma upper
limits of w = 19.64 to 19.93 (inter-quartile).

We thank the staff of the Observatorio AstronÃ³mico Nacional in San Pedro
MÃ¡rtir.


GRB_name: GRB210606A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30136
SUBJECT: GRB 210606A: Swift ToO observations
DATE:    21/06/06 21:12:22 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the Swift/BAT GRB 210606A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021451

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210606B
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30138
SUBJECT: GRB 210606B: GECAM detection
DATE:    21/06/07 05:18:31 GMT
FROM:    Ce Cai at IHEP  <caice@ihep.ac.cn>

C. Cai, Y. Huang, S. L. Xiong, S. L. Xie, S. Xiao, Y. Zhao, J. C. Liu,
C. Y. Li, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li, X. H. Liang,
J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu, Q. Luo, X. Ma,
G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi, L. M. Song,
X. Y. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, C. W. Wang, J. Z. Wang,
P. Wang, X. Y. Wen, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao, Q. B. Yi,
B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang,
K. Zhang, P. Zhang, S. N. Zhang, Z. Zhang, S. Y. Zhao,  S. J. Zheng,
X. Zhou (IHEP), report on behalf of GECAM team:

During the commissioning phase, GECAM-B was triggered by a long GRB 210606B
at 2021-06-06T22:41:08.100 UTC (denoted as T0), 
which was also observed by Fermi/GBM (trigger #644712030); 
AGILE (trigger #550104073); INTEGRAL/SPIACS (trigger #9256).

GECAM alert data was promptly downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
The time latency of the first BeiDou message relative to the trigger time
is about 1 minute.

According to the BDS alert data, this burst mainly consists of 
multiple pulses with a duration of about 35s.  

An automatic on-ground localization was calculated using the light curves
and spectrum. Although the in-flight calibration of energy response and
localization has not been finalized yet, GECAM-B localized this burst to
the following position (J2000):
ra: 85.89 deg
dec: -18.63 deg
err: 1.39 deg (1-sigma, statistical only)
The current systematic error of location is estimated to be several degrees
which could be minimized by the ongoing calibration. 

This position is consistent with the Fermi GBM team localization 
(trigger #644712030) within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_76718468.png

As the detailed science data are downloaded, all analyses would be improved.

Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.

Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).


GRB_name: GRB210606B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30139
SUBJECT: GRB 210606B: BALROG localization (Fermi Trigger 644712030 / GRB 210606945)
DATE:    21/06/07 05:51:43 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

F. Kunzweiler, B. Biltzinger, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
644712030 at 22:40:25 on 06 June 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 87.9+/-0.5 deg
Decl.(2000.0) = -15.9+/-0.6 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210606945/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210606945/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210606945/json

                        


GRB_name: GRB210606A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30141
SUBJECT: GRB 210606A: 1.5m OSN optical upper limit
DATE:    21/06/07 11:02:31 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

T.-R. Sun, Y.-D. Hu, A. J. Castro-Tirado, V. Casanova, M. D. Caballero-Garcia, M. A. Castro Tirado and E. Fernandez-Garcia (IAA-CSIC), on behalf of a larger collaboration, report:

Following the detection of GRB 210606A by both Fermi (Fermi/GBM GCNC 30131) and Swift (DeLaunay et al. GCNC 30134), we triggered the 1.5m OSN telescope in Granada (Spain) starting on June 6 at 21:08 UT (i.e. ~17.2 h post burst) in order to cover the Swift/BAT error region. Images were taken in BVRI bands. No optical afterglow is detected in the error box down to R=22.2 in the combined (3x600s) image, which is in agreement with the non-detections reported by Lipunov et al. (GCNC 30132) and Pereyra et al. (GCNC 30135).

We thank the staff at OSN for their excellent support.


GRB_name: GRB210606B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30142
SUBJECT: GRB 210606B: AGILE detection
DATE:    21/06/07 11:44:52 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), F. Verrecchia, C. Pittori (SSDC, and INAF/OAR), M.
Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C.
Casentini, Y. Evangelista, G. Piano (INAF/IAPS), F. Lucarelli (SSDC, and
INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino, N.
Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and Bergen
University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma (ASI), F.
Longo (Univ. Trieste and INFN Trieste), A. Giuliani (INAF/IASF-Mi), report
on behalf of the AGILE Team:

The AGILE satellite detected the long GRB 210606B at T0 = UTC 2021-06-06
22:41:03 s (UTC), reported by Fermi/GBM (Trigger no. 644712030), GECAM (GCN
#39138), and BALROG (GCN #39139).

The burst is visible in the AGILE scientific ratemeters of the SuperAGILE
(SA; 20-60 keV), MiniCALorimeter (MCAL; 0.4-100 MeV), and AntiCoincidence
(AC; 50-200 keV) detectors. The event lasted ~35 s and released a total
number of 3120 counts in the SA detector (above a background rate of 66
Hz), 43110 counts in the MCAL detector (above a background rate of 1250
Hz), and 125100 counts in the AC detector (above a background rate of 3660
Hz). The AGILE ratemeter light curves can be found at
http://www.agilescienceapp.it/notices/GRB210606B_AGILE_RM.png .

The event also triggered a partial high time resolution MCAL data
acquisition at T = UTC 2021-06-06 22:41:13.18 +/- 0.01 s, whose light curve
can be found at:
http://www.agilescienceapp.it/notices/073374_GRB_550104073.181294.png .

Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.


GRB_name: GRB210605A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30143
SUBJECT: IPN triangulation of GRB 210605A (short)
DATE:    21/06/07 12:34:39 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, report:

The bright, short-duration GRB 210605A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30127)
was detected by Fermi (GBM trigger 644562543), Konus-Wind,
INTEGRAL (SPI-ACS), and Swift (BAT) at about 18538 s UT (05:08:58).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    21.609 (01h 26m 26s) -45.089 (-45d 05' 19")
  Corners:
    24.666 (01h 38m 40s) -49.385 (-49d 23' 08")
    19.468 (01h 17m 52s) -41.356 (-41d 21' 22")
    19.355 (01h 17m 25s) -41.513 (-41d 30' 47")
    24.633 (01h 38m 32s) -49.663 (-49d 39' 47")
  ---------------------------------------------
The error box area is 1.2 sq. deg, and its maximum
dimension is 9.0 deg (the minimum one is 8.4 arcmin).
The Sun distance was 81 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210605_T18539/IPN

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210605A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30144
SUBJECT: Konus-Wind detection of GRB 210605A (short/hard)
DATE:    21/06/07 13:07:38 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The short/hard GRB 210605A (Fermi GBM Final Real-time Localization:
Fermi GBM team, GCN 30127; IPN localization: Svinkin et al., GCN 30143)
triggered Konus-Wind (KW) at T0=18539.058 s UT (05:08:59.058).

The burst light curve shows a single, hard-spectrum pulse,
which starts at ~T0-0.038 s, peaks at ~T0-0.032 s,
and has the total duration of ~0.35 s (T100, 20-1500 keV).
The emission in this pulse is seen up to ~10 MeV.
In the soft 20-100 keV KW band, we note a hint for an extended emission up to ~T0+25 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210605_T18539/

As observed by Konus-Wind, the burst had
a fluence of (4.2 Â± 1.1)x10^-6 erg/cm^2 and
a 16-ms peak energy flux, measured from T0-0.032,
of (5.7 Â± 1.4)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst (measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.75(-0.18,+0.21) and Ep = 2079(-614,+986) keV (chi2 = 23/44 dof).
Fitting this spectrum by a Band function yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.1 (chi2 = 23/43 dof).

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210602A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30145
SUBJECT: Konus-Wind detection of GRB 210602A
DATE:    21/06/07 15:08:45 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin,
A. Ridnaya, A. Tsvetkova,  M. Ulanov, and T. Cline, report:

The bright GRB 210602A (MAXI/GSC detection: Serino et al., GCN 30113;
CALET Gamma-Ray Burst Monitor detection: Pal'shin et al., GCN 30117)
triggered Konus-Wind (KW) at T0=43439.748 s UT (12:03:59.748).

The burst light curve shows a single pulse which starts at ~T0-0.5 s,
peaks at ~T0+0.512 s, and has the total duration of ~3.1 s (T100, 20-1500 keV).
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210602_T43439/

As observed by Konus-Wind, the burst had
a fluence of (6.3 Â± 0.6)x10^-6 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+0.384,
of (9.5 Â± 1.0)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.25(-0.23,+0.26) and Ep = 188(-33,+58) keV (chi2 = 75/97 dof).
Fitting this spectrum by a Band function yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 75/96 dof).

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210605B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30146
SUBJECT: GRB 210605B: Swift-XRT observations
DATE:    21/06/07 18:29:21 GMT
FROM:    Boris Sbarufatti at PSU  <bxs60@psu.edu>

A. D'Ai (INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU),
D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), T.
Sbarrato (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of
the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Swift/BAT-detected burst GRB 210605B (James DeLaunay et al. GCN Circ.
30130), collecting 5.0 ks of Photon Counting (PC) mode data between
T0+74.2 ks and T0+96.6 ks. 

One uncatalogued X-ray sources has been detected, however it is not
above the RASS limit or shows definitive signs of fading. Therefore, at
the present time we cannot confirm if this source is the afterglow.
Details of the source are given below:

Source 1:
  RA (J2000):  15.7456  =  01:02:58.95
  Dec (J2000): -6.4290  =  -06:25:44.3
  Error: 5.7 arcsec (radius, 90% conf.)
  Count-rate: (2.94 [+1.05, -0.86])e-3 ct s^-1  
  Distance: 145 arcsec from Swift/BAT position.
  Flux: (9.3 [+3.3, -2.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The field has been previously observed by XRT for the Swift
Gravitational Wave Galaxy Survey (https://www.swift.ac.uk/SGWGS/). No
source was detected at this position on a 5.3 ks integrated exposure,
down to a 3-Ïƒ upper limit of 2.7 e-3 ct s^-1.

A catalogued source and a spurious source caused by Earth limb
contamination were also detected.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021450.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210606B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30147
SUBJECT: GRB 210606B: Fermi GBM detection
DATE:    21/06/07 22:12:01 GMT
FROM:    Christian Malacaria at NASA-MSFC/USRA  <cmalacaria@usra.edu>

C. Malacaria (USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 22:40:25.32 UT on 6 June 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210606B (trigger 644712030 / 210606945).
This burst was also independently detected by INTEGRAL SPI-ACS,
GECAM (GCN 30138) and AGILE (GCN 30142).

The on-ground calculated location, using the GBM trigger
data, is RA = 87.48, DEC = -18.41 (J2000 degrees,
equivalent to 05 h 49 m, -18 d 24 '), with a statistical uncertainty
of 1.20 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).

The angle from the Fermi LAT boresight at the GBM trigger time is 82 degrees.

The GBM light curve consists of three main peaks
taking place about 40 s after the initial trigger,
plus one weaker peak showing 250 s after the initial trigger.
The full event has a duration (T90) of about 244 s (50-300 keV).

The time-averaged spectrum from T0+42 s to T0+52 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.04 +/- 0.01 and
the cutoff energy, parameterized as Epeak, is 397 +/- 13 keV.
A Band function fits the spectrum equally well
with Epeak= 394 +/- 14 keV, alpha = -1.04 +/- 0.01 and beta = -3.7 +/- 1.5 .

The event fluence (10-1000 keV) in this time interval is
(3.45 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+49 s in the 10-1000 keV band
is 35.6 +/- 0.4 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"


GRB_name: GRB210606B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30154
SUBJECT: IPN triangulation of GRB 210606B
DATE:    21/06/08 19:34:53 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. V. Golovin, A. S. Kozyrev, M. L. Litvak,
and A. B. Sanin, on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, D. Frederiks, A. Ridnaia,
A. Lysenko, and T. Cline on behalf of the Konus-Wind team,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu
on behalf of the Swift-BAT team, and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The bright, long-duration 210606B
(GECAM detection: Cai et al., GCN Circ. 30138;
BALROG localization: Kunzweiler et al., GCN Circ. 30139;
AGILE detection: Ursi et al., GCN Circ. 30142;
Fermi-GBM detection: The Fermi GBM team, GCN Circ. 30147)
was detected by Fermi (GBM trigger 644712030), Konus-Wind,
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), GECAM, AGILE (SA, MCAL, and AC)
and Swift (BAT) at about 81625 s UT (22:40:25)
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    87.986 (05h 51m 57s) -16.689 (-16d 41' 19")
  Corners:
    86.597 (05h 46m 23s) -15.596 (-15d 35' 45")
    89.249 (05h 57m 00s) -17.675 (-17d 40' 30")
    89.394 (05h 57m 35s) -17.719 (-17d 43' 07")
    86.742 (05h 46m 58s) -15.651 (-15d 39' 05")
  ---------------------------------------------
The error box area is 588 sq. arcmin, and its maximum
dimension is 3.4 deg (the minimum one is 3 arcmin).
The Sun distance was 40 deg.

This box may be improved.

The IPN localization is consistent with, but reduces the area of, the
Fermi RoboBA and BALROG localizations (GCN Circ. 30147 and 30139).

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210606_T81665/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.


GRB_name: GRB210606B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30157
SUBJECT: Konus-Wind detection of GRB 210606B
DATE:    21/06/09 10:06:48 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 210606B (GECAM detection: Cai et al., GCN 30138;
BALROG localization: Kunzweiler et al., GCN Circ. 30139;
AGILE detection: Ursi et al., GCN 30142;
Fermi GBM detection:  Malacaria & Meegan, GCN 30147;
IPN localization: Hurley et al., GCN Circ. 30154;)
triggered Konus-Wind (KW) at T0=81665.249 s UT (22:41:05.249).

The burst light curve contains two major emission episodes:
a bright, multi-peaked emission complex in the interval from ~T0-2 s to ~T0+30 s;
and the second, much weaker episode, which starts at ~T0+195 s, and has a duration of ~70 s.
The emission in the main episode is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210606_T81665/

As observed by Konus-Wind, the burst had
a fluence of (8.1 Â± 0.7)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 4.224 s,
of (1.7 Â± 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The spectrum of the main episode (measured from T0 to T0+33.024 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.04 (-0.06,+0.07),
the high energy photon index beta = -2.61 (-0.54,+0.24),
the peak energy Ep = 309 (-27,+31) keV,
chi2 = 80/97 dof.

The spectrum of the second episode (measured from T0+193.536 to T0+259.072 s)
is best fit in the 20 keV - 20 MeV range
by the a simple power law with the photon index of 2.1 (-0.14,+0.15), chi2 = 94/99 dof.

The spectrum near the peak count rate (measured from T0+0.256
to T0+13.824 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.08 (-0.07,+0.08),
the high energy photon index beta = -2.67 (-1.76,+0.33),
the peak energy Ep = 345 (-42,+48) keV,
chi2 = 84/97 dof.

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210605A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30158
SUBJECT: GRB 210605A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/06/09 10:16:53 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

S. Sugita, A. Yoshida, T. Sakamoto, V. Pal'shin (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The short GRB 210605A (Fermi GBM Final Real-time Localization: Fermi GBM
team, GCN Circ. 30127; IPN localization: Svinkin et al., GCN Circ. 30143;
Konus-Wind detection: Frederiks et al., GCN Circ. 30144;
https://gcn.gsfc.nasa.gov/other/210605A.gcn3) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 05:08:58.441 UTC on 5 June 2021.
The burst signal was seen by all CGBM detectors.
No real-time CGBM GCN notice was distributed about this trigger because
the real-time communication from the ISS was off (loss of signal).

The burst light curve shows a multi-peaked pulse which starts at
T-0.096 sec, peaks at -0.032 sec and ends at T+0.240 sec.
The T90 and T50 durations measured by the SGM data are 0.304 +- 0.051 sec
and 0.144 +- 0.045 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1306904781/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.


GRB_name: GRB210607B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30159
SUBJECT: GRB 210607B: Insight-HXMT/HE detection
DATE:    21/06/10 03:22:35 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

Y. Q. Zhang, C. Zheng, C. Cai, J. C. Liu, Q. Luo,  
W. C. Xue, Q. B. Yi,  Y. Huang, C. K. Li, S. Xiao,
G. Li, X. B. Li, J. Y. Liao, X. Y. Song, S. L. Xiong, C. Z. Liu, 
X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, 
X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), 
T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, 
M. Wu, Y. P. Xu, S. N. Zhang (IHEP), 
report on behalf of the Insight-HXMT team:

At 2021-06-07T18:37:17.800 (T0), Insight-HXMT/HE detected 
GRB 210607B (trigger ID: HEB210607775) in a routine search of the data.

The Insight-HXMT/HE light curve mainly consists of single
pulse with a duration (T90) of 3.19 s measured from T0-0.48 s. 
The 1-ms peak rate, measured from T0+0.04 s, is 1825 cnts/sec. 
The total counts from this burst is 2993 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210607775_lc.jpg

All measurements above are made with the CsI detectors operating in the 
regular mode with the energy range of about 80-800 keV (deposited energy). 
Only gamma-rays with energy greater than about 200 keV can penetrate 
the spacecraft and leave signals in the CsI detectors installed inside 
of the telescope. 

Insight-HXMT is the first Chinese space X-ray telescope, which was 
funded jointly by the China National Space Administration (CNSA) and 
the Chinese Academy of Sciences (CAS). 
More information about it could be found at: 
http://www.hxmt.org.


GRB_name: GRB210610A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30160
SUBJECT: GRB 210610A: Swift detection of a burst with an optical counterpart
DATE:    21/06/10 15:26:44 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

K. L. Page (U Leicester), M. A. Baer (PSU), J.D. Gropp (PSU),
N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 15:03:43 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210610A (trigger=1054627).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 204.285, +14.480 which is 
   RA(J2000) = 13h 37m 08s
   Dec(J2000) = +14d 28' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 15 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 15:05:13.3 UT, 90.0 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 204.2823, 14.4652 which
is equivalent to:
   RA(J2000)  = 13h 37m 07.76s
   Dec(J2000) = +14d 27' 54.7"
with an uncertainty of 2.2 arcseconds (radius, 90% containment). This
location is 54 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at https://www.swift.ac.uk/sper. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 93 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 13:37:07.62 = 204.28174
  DEC(J2000) = +14:27:55.0  =  14.46528
with a 90%-confidence error radius of about 0.61 arc sec. This position is 2.2
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.12 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.032. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210610A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30161
SUBJECT: GRB 210610A: MITSuME Akeno optical observation
DATE:    21/06/10 16:13:57 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, K. L. Murata, M. Niwano, N. Ito, H. Takamatsu, Y. Imai,
S. Sato, M. Takaku, R. Noto, R. Yamaguchi, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210610A (K. L. Page et al. GCN
Circular #30160) with the optical three color (g', Rc, and Ic) CCD
cameras attached to the
MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The
observation with a series of 10 sec exposures started at 2021-06-10
15:04:41 UT (58 seconds after Swift BAT trigger). We stacked the
images with good conditions. We detected the point source at the
position consistent with the afterglow detected previously (K. L. Page
et al. GCN Circular #30160)
We measured the magnitudes as follows.

filter MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
g' 15:08:47 10 16.4+/-0.4
Rc 15:08:29 50 15.3+/-0.1
Ic 15:08:29 50 15.0+/-0.2
------------------------------------------------------------------------------------------------
T-EXP: Total Exposure time

We used PS1 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU
reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages
4-24; https://github.com/MNiwano/Eclaire).


GRB_name: GRB210610A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30162
SUBJECT: GRB 210610A: Xinglong-2.16m optical afterglow observations
DATE:    21/06/10 16:20:29 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

D. Xu, Z.P. Zhu, S.Y. Fu, X. Liu (NAOC) report on behalf of a larger 
collaboration:

We observed the field of GRB 210610A (Page et al., GCN 30160) using the 
2.16-m optical telescope located at Xinglong, Hebei, China, equipped 
with the BFOSC camera. Observations started at 15:28:02 UT on 
2021-06-10, i.e., 24.25 min after the burst.

An uncatalogued and varying optical transient is detected at coordinates:

R.A. (J2000) = 13:37:07.60
Dec. (J2000) = +14:27:55.0

with an error radius of ~ 0.3 arsec, positionally being well consistent 
with the Swift/UVOT detection (Page et al., GCN 30160). The OT is thus 
the optical afterglow of the GRB, and it has r = 16.97 +/- 0.01 mag at 
26.25 min post-burst, calibrated with the nearby PanSTAR field.

Spectroscopy of the afterglow is underway.


GRB_name: GRB210610A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30163
SUBJECT: GRB 210610A: GIT optical detection
DATE:    21/06/10 16:57:26 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), V. Bhalerao(IITB), U. Stanzin (IAO), G. C. Anupama(IIA), S.
Barway(IIA) report on behalf of the GIT team:

We observed GRB 210610A detected by Swift-BAT ( K. L. Page et al., GCN
#30160, optical counterpart reported by R. Hosokawa et al., GCN #30161 and
D. Xu et al., GCN #30162), with the 0.7m GROWTH-India Telescope (GIT). We
obtained a 300-sec exposure in the r' filter. We clearly detected the
afterglow in our image at R.A.= 13:37:07.64 and DEC.= 14:27:55.10. The
photometric results follow as:

-------------------------------------------------------------------

 JD (start) | T_mid-T0(hrs) | Filter | Magnitude (AB) |

-------------------------------------------------------------------

2459376.178 | 1.22 | r' |  18.79+/- 0.05 |

-------------------------------------------------------------------

The magnitudes are calibrated against PanSTARRS DR1 (Flewelling et al., 2018)
and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics and the
Indian Institute of Technology Bombay with support from the Indo-US Science
and Technology Forum (IUSSTF) and the Science and Engineering Research
Board (SERB) of the Department of Science and Technology (DST), Government
of India (https://sites.google.com/view/growthindia/). It is located at the
Indian Astronomical Observatory (Hanle), operated by the Indian Institute
of Astrophysics (IIA).


GRB_name: GRB210610A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30164
SUBJECT: GRB 210610A: Xinglong-2.16m redshift
DATE:    21/06/10 17:26:59 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu, D. Xu, S.Y. Fu, X. Liu (NAOC) report on behalf of a larger 
collaboration:

Following the photometry of the optical afterglow (Xu et al., GCN 30162) 
of GRB 210610A (Page et al., GCN 30160), we carried out 2x1800 s 
spectroscopy of the afterglow using the BFOSC camera. The spectrum 
covers the wavelength range 4000-9000 AA. The observation mid time is 
2021 June 10.667 UT, i.e., 0.955 hr after the burst.

In our spectra, continuum is detected over the whole observed range. A 
prominent absorption feature is detected around 5519 AA, which we 
identify as Ly alpha in absorption, and blueward of which is Ly alpha 
forest. The interpretation is confirmed by the detection of metal 
absorption lines such as Si II, Si IV, C IV, all at a common redshift z 
= 3.54, using old calibrations. The redshift measurement may be improved 
a bit when new calibrations are available.

We thank the excellent support of the Xinglong-2.16m staff, especially 
Junjun Jia and Jie Zheng.


GRB_name: GRB210610A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30165
SUBJECT: GRB 210610A: Enhanced Swift-XRT position
DATE:    21/06/10 18:08:33 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 792 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210610A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 204.28211, +14.46540 which is equivalent
to:

RA (J2000): 13h 37m 7.71s
Dec (J2000): +14d 27' 55.4"

with an uncertainty of 2.3 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.


GRB_name: GRB210610A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30166
SUBJECT: Swift GRB 210610A: MASTER optical counterpart observation
DATE:    21/06/10 18:47:50 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, K.Zhirkov, V.Kornilov, E.Gorbovskoy, I.Gorbunov,P.Balanutsa,V.Vladimirov,A.Kuznetsov,
D. Vlasenko, N.Tiurina, D.Zimnukhov, V.Senik, V.Topolev, A.Chasovnikov, D.Cheryasov (Lomonosov MSU,SAI,PhysicsDepartment),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER Global robotic net (MASTER-Net:http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
started Swift GRB 210610A (Page et al. GCN 30160) error box observation 
at 2021-06-10 16:23:35UT at MASTER-SAAO.

There is MASTER OT J133707.60+142755.0 with m_OT~20.1m (unfiltered), that was 
discovered by Swift-UVOT (Page et al. 30160) and confirmed by
Hosokawa et al. GCN 30161, Xu et al. GCN 30162, Kumar et al. GCN 30163, 
and with redshift z=3.54 detected by Zhu et al. GCN 30164.

Observation and reduction will be continued.


GRB_name: GRB210610A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30167
SUBJECT: Swift GRB 210610A: Global MASTER-Net observations report 
DATE:    21/06/10 18:47:58 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-SAAO robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210610A ( K. L. Page et al., GCN 30160) errorbox  4610 sec after notice time and 4632 sec after trigger time at 2021-06-10 16:20:55 UT, with upper limit up to  17.1 mag. Observations started at twilight.  The observations began at zenith distance = 58 deg. The sun  altitude  is -8.5 deg. 

The galactic latitude b = 73 deg., longitude l = 346 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1633161

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    4662 |         MASTER-SAAO |   C |    60 | 16.8 |        
    4742 |         MASTER-SAAO |   C |    60 | 16.9 |        
    4822 |         MASTER-SAAO |   C |    60 | 17.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210610A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30168
SUBJECT: GRB210610A: MeerLICHT multi-colour photometry
DATE:    21/06/10 18:56:04 GMT
FROM:    Paul Vreeswijk at Radboud U/Nijmegen  <p.vreeswijk@astro.ru.nl>

S. de Wet (UCT), P.M. Vreeswijk (Radboud), P.J. Groot
(Radboud/UCT/SAAO), A. Levan (Radboud) report on behalf of the
MeerLICHT consortium:

Following the detection of GRB210610A by Swift and its optical
counterpart (Page et al., GCN 30160), reported at a redshift of z=3.54
by Zhu et al. (GCN 30163), the 0.6m MeerLICHT telescope, located at
Sutherland, South Africa began observations of the field at
2021-06-10, 16:48:47 UT with a repeating sequence of optical filters:
q,u,q,g,q,r,q,i,q,z, at 60s integration time each. The q-band
wavelength limits are 440-720nm.

First detections are:
q_AB = 19.60 +/- 0.08 +/- 0.02 at 16:48:47 UT
r_AB = 19.09 +/- 0.10 +/- 0.01 at 16:56:12 UT
i_AB = 18.74 +/- 0.12 +/- 0.02 at 16:59:10 UT
z_AB = 18.37 +/- 0.19 +/- 0.02 at 17:02:09 UT, 
where the first uncertainty on the magnitude is the statistical
uncertainty and the second is the uncertainty on the photometric
calibration.

In g-band the afterglow is detected only once, at 17:08:11 UT, at
g_AB = 20.18 +/- 0.18 +/- 0.03, close to the limiting magnitude of the
frame. 

The source is not detected in the u-band, starting at 16:50:11 UT, at
a 5-sigma limiting magnitude of u_AB > 18.76.

Further fading of the source is observed during the ongoing sequence. 

MeerLICHT is built and run by a consortium consisting of Radboud
University, the University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester
and the University of Amsterdam. 


GRB_name: GRB210610A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30169
SUBJECT: GRB 210610A: MITSuME Ishigaki optical observation
DATE:    21/06/10 19:54:13 GMT
FROM:    Takashi Horiuchi at Ishigakijima Astronomical Obs  <takashi.horiuchi@nao.ac.jp>

Takashi Horiuchi, Hidekazu Hanayama (NAOJ), Katsuhiro L. Murata,
Yoichi Yatsu, Nobuyuki Kawai (Tokyo Tech) report on behalf of the
MITSuME collaboration:

We observed the field of GRB 210610A (K. L. Page et al. GCN
Circular #30160)  with the optical three
color (g', Rc, and Ic) CCD cameras attached to the 105 cm
Murikabushi telescope of Ishigakijima Astronomical Observatory,
Okinawa, Japan.

The observation with a series of 60 sec exposures started on
2021-06-10 15:40:04 UT (37 min after Swift BAT trigger).
We detected the point source at the position consistent with
the afterglow reported by K. L. Page et al. GCN Circular #30160.
Here, we removed bad data (images) with wrong sky conditions
and obtained the magnitudes as follows:

T0+[min] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
37 2021-06-10T15:57:45  900 (60s Ã— 15)  g'=19.41+/-0.14, Rc=18.19+/-0.04, Ic=17.73+/-0.10
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
The SDSS catalog (DR16) is used for flux calibration.


GRB_name: GRB210610B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30170
SUBJECT: GRB 210610B: Swift detection of a burst with bright optical afterglow
DATE:    21/06/10 20:06:36 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

K. L. Page (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 19:51:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210610B (trigger=1054681).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 243.939, +14.391 which is 
   RA(J2000) = 16h 15m 45s
   Dec(J2000) = +14d 23' 29"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a comlex
structure with a duration of about 100 sec.  The peak count rate
was ~11000 counts/sec (15-350 keV), at ~8 sec after the trigger. 

The XRT began observing the field at 19:52:51.4 UT, 83.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 243.9180, 14.3977 which is equivalent to:
   RA(J2000)  = 16h 15m 40.32s
   Dec(J2000) = +14d 23' 51.7"
with an uncertainty of 6.7 arcseconds (radius, 90% containment). This
location is 77 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

The initial flux in the 0.1 s image was 1.07e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 91 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 16:15:40.41 = 243.91836
  DEC(J2000) = +14:23:56.7  =  14.39909
with a 90%-confidence error radius of about 0.61 arc sec. This position is 5.2
arc sec. from the center of the XRT error circle. The estimated magnitude is
13.70 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.044. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)


GRB_name: GRB210610B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30171
SUBJECT: GRB 210610B: BALROG localization (Fermi Trigger 645047470 / GRB 210610827)
DATE:    21/06/10 20:12:28 GMT
FROM:    Jochen Greiner at MPE,Garching  <jcg@mpe.mpg.de>

B. Biltzinger, F. Kunzweiler, F. Berlato, J. Burgess & J. Greiner (all MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
645047470 at 19:51:05 on 10 June 2021 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position (1 sigma statistical errors) is:
RA(2000.0) = 244.2+/-0.6 deg
Decl.(2000.0) = 16.5+/-1.2 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210610827/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB210610827/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210610827/json

                        


GRB_name: GRB210606A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30172
SUBJECT: GRB 210606A: Swift-XRT afterglow detection
DATE:    21/06/10 20:13:23 GMT
FROM:    Aaron Tohuvavohu at U Toronto  <aaron.tohu@gmail.com>

B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU), K.L. Page
(U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB),
T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the Swift/BAT-GUANO
detected burst GRB 210606A (James DeLaunay et al. GCN Circ. 30134),
collecting 7.3 ks of Photon Counting (PC) mode data between T0+62.3 ks
and T0+385.7 ks. 

Four uncatalogued X-ray sources are detected consistent with being
within 394 arcsec of the Swift/BAT position, of which one ("Source 1")
is fading with 4.6-sigma significance, and is therefore likely the GRB
afterglow. Using 4521 s of PC mode data and 5 UVOT images, we find an
enhanced XRT position (using the XRT-UVOT alignment and matching UVOT
field sources to the USNO-B1 catalogue): RA, Dec = 170.94110, +0.81293
which is equivalent to:

RA (J2000): 11h 23m 45.86s
Dec(J2000): +00d 48' 46.5"

with an uncertainty of 2.3 arcsec (radius, 90% confidence). This
position is 6.1 arcmin from the Swift/BAT position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.1 (+0.9, -0.6).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+0.5, -0.4). The
best-fitting absorption column is  1.4 (+1.6, -1.0) x 10^21 cm^-2,
consistent with the Galactic value of 3.8 x 10^20 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 3.5 x 10^-11 (4.3 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.4 (+1.6, -1.0) x 10^21 cm^-2
Galactic foreground: 3.8 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.8 (+0.5, -0.4)

The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/ToO_GRBs/00021451/Source1.php.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021451.

This circular is an official product of the Swift-XRT team.


GRB_name: GRB210610B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30174
SUBJECT: GRB 210610B: GIT optical detection
DATE:    21/06/10 20:45:52 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), J. Stanzin (IAO), V. Bhalerao(IITB), G. C. Anupama(IIA), S.
Barway(IIA) report on behalf of the GIT team:

We observed GRB 210610B detected by Swift-BAT (K. L. Page et al., GCN
#30170), with the 0.7m GROWTH-India Telescope (GIT). We obtained a
60-sec exposure
in the r' filter. We clearly detected the afterglow in our image at
R.A.= 16:15:40.44
and DEC.= +14:23:56.65 with an uncertainty of ~0.67 arcsec. The photometric
results follow as:

-------------------------------------------------------------------

 JD (start) | T_mid-T0(hrs) | Filter | Magnitude (AB) |

-------------------------------------------------------------------

2459376.3429 | 0.37 | r' |  15.98 +/- 0.1 |

-------------------------------------------------------------------

The magnitudes are calibrated against PanSTARRS (Flewelling et al., 2018)
and not corrected for Galactic extinction.

The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics and the
Indian Institute of Technology Bombay with support from the Indo-US Science
and Technology Forum (IUSSTF) and the Science and Engineering Research
Board (SERB) of the Department of Science and Technology (DST), Government
of India (https://sites.google.com/view/growthindia/). It is located at the
Indian Astronomical Observatory (Hanle), operated by the Indian Institute
of Astrophysics (IIA).


GRB_name: GRB210610B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30175
SUBJECT: GRB 210610B: CrAO/ZTSh optical observations
DATE:    21/06/10 20:50:39 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

V. Rumyantsev (CrAO), A. Pozanenko (IKI),  S. Belkin (IKI), N. Pankov 
(HSE) report on behalf of GRB IKI FuN:

We observed  the GRB 210610B (Page et al., GCN  30170)  with ZTSh 2.6m 
telescope of CrAO observatory starting on June., 10 (UT) 20:19:24.  We 
detect the bright optical afterglow (Page et al., GCN  30170). We 
continue observations and will report photometry after data receiving.


GRB_name: GRB210610B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30176
SUBJECT: Swift GRB 210610B: Global MASTER-Net observations report 
DATE:    21/06/10 21:15:40 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, 
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov,  D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),

R. Podesta, C.Lopez, F. Podesta, C.Francile 
(Observatorio Astronomico Felix Aguilar OAFA),

R. Rebolo, M. Serra 
(The Instituto de Astrofisica de Canarias),

D. Buckley 
(South African Astronomical Observatory),

O.A. Gres, N.M. Budnev, O.Ershova 
(Irkutsk State University, API),

A. Tlatov, D. Dormidontov 
(Kislovodsk Solar Station of the Pulkovo Observatory),

V. Yurkov, A. Gabovich, Yu. Sergienko 
(Blagoveschensk Educational State University)




MASTER-Kislovodsk robotic telescope  (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L)  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210610B ( K. L. Page et al., GCN 30170) errorbox 145 sec after trigger time at 2021-06-10 19:53:52 UT, with upper limit up to  18.9 mag. The observations began at zenith distance = 30 deg. The sun  altitude  is -21.6 deg. 

MASTER-SAAO robotic telescope  located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 210610B errorbox  0 sec after notice time and 582 sec after trigger time at 2021-06-10 20:01:10 UT, with upper limit up to  19.2 mag. The observations began at zenith distance = 52 deg. The sun  altitude  is -54.2 deg. 

MASTER-Tavrida robotic telescope  located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210610B errorbox  15 sec after notice time and 598 sec after trigger time at 2021-06-10 20:01:25 UT, with upper limit up to  20.3 mag. The observations began at zenith distance = 31 deg. The sun  altitude  is -19.1 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210610B errorbox  3486 sec after notice time and 4069 sec after trigger time at 2021-06-10 20:59:16 UT, with upper limit up to  17.6 mag. Observations started at twilight.  The observations began at zenith distance = 44 deg. The sun  altitude  is -12.3 deg. 

The galactic latitude b = 40 deg., longitude l = 29 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1633397

We obtain a following upper limits.  

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

     160 |   MASTER-Kislovodsk |   C |    30 | 17.5 |        
     215 |   MASTER-Kislovodsk |   C |    40 | 17.7 |        
     643 |         MASTER-SAAO | P\  |   120 | 18.3 |        
     798 |         MASTER-SAAO | P\  |   430 | 19.0 |  Coadd 
     658 |      MASTER-Tavrida |   C |   120 | 19.1 |        
     838 |      MASTER-Tavrida |   C |   480 | 20.0 |  Coadd 
     658 |      MASTER-Tavrida |   C |   120 | 19.1 |        
     722 |   MASTER-Kislovodsk |   C |   130 | 18.2 |        
     722 |   MASTER-Kislovodsk |  P| |   130 | 18.3 |        
     792 |         MASTER-SAAO | P\  |   140 | 18.4 |        
     813 |      MASTER-Tavrida |   C |   150 | 19.2 |        
     813 |      MASTER-Tavrida |   C |   150 | 19.1 |        
     967 |         MASTER-SAAO | P\  |   170 | 18.5 |        
     997 |      MASTER-Tavrida |   C |   180 | 19.2 |        
     997 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    1161 |         MASTER-SAAO | P\  |   180 | 18.5 |        
    1341 |         MASTER-SAAO | P\  |   540 | 19.1 |  Coadd 
    1197 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    1359 |   MASTER-Kislovodsk |   C |   180 | 13.7 |        
    1359 |   MASTER-Kislovodsk |  P| |   180 | 18.5 |        
    1361 |         MASTER-SAAO | P\  |   180 | 18.6 |        
    1403 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    1403 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    1560 |         MASTER-SAAO | P\  |   180 | 18.5 |        
    1603 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    1603 |      MASTER-Tavrida |   C |   180 | 19.3 |        
    1760 |         MASTER-SAAO | P\  |   180 | 18.6 |        
    1940 |         MASTER-SAAO | P\  |   540 | 19.2 |  Coadd 
    1802 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    1802 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    1959 |         MASTER-SAAO | P\  |   180 | 18.7 |        
    2001 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    2181 |      MASTER-Tavrida |   C |   540 | 20.2 |  Coadd 
    2001 |      MASTER-Tavrida |   C |   180 | 19.1 |        
    2019 |   MASTER-Kislovodsk |   C |   180 | 18.2 |        
    2019 |   MASTER-Kislovodsk |  P| |   180 | 18.9 |        
    2159 |         MASTER-SAAO | P\  |   180 | 18.5 |        
    2201 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    2201 |      MASTER-Tavrida |   C |   180 | 19.3 |        
    2358 |         MASTER-SAAO | P\  |   180 | 18.6 |        
    2401 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    2401 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    2558 |         MASTER-SAAO | P\  |   180 | 16.5 |        
    2600 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    2780 |      MASTER-Tavrida |   C |   540 | 20.3 |  Coadd 
    2600 |      MASTER-Tavrida |   C |   180 | 19.3 |        
    2743 |   MASTER-Kislovodsk |   C |   180 | 13.8 |        
    2743 |   MASTER-Kislovodsk |  P| |   180 | 18.9 |        
    2757 |         MASTER-SAAO | P\  |   180 | 15.7 |        
    2800 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    2800 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    2957 |         MASTER-SAAO | P\  |   180 | 17.3 |        
    2999 |      MASTER-Tavrida |   C |   180 | 19.7 |        
    2999 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    3156 |         MASTER-SAAO | P\  |   180 | 16.6 |        
    3199 |      MASTER-Tavrida |   C |   180 | 18.8 |        
    3379 |      MASTER-Tavrida |   C |   540 | 19.9 |  Coadd 
    3199 |      MASTER-Tavrida |   C |   180 | 18.3 |        
    3356 |         MASTER-SAAO | P\  |   180 | 17.2 |        
    3398 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    3398 |      MASTER-Tavrida |   C |   180 | 18.9 |        
    3418 |   MASTER-Kislovodsk |   C |   180 | 18.3 |        
    3418 |   MASTER-Kislovodsk |  P| |   180 | 18.8 |        
    3555 |         MASTER-SAAO | P\  |   180 | 17.0 |        
    3598 |      MASTER-Tavrida |   C |   180 | 19.6 |        
    3598 |      MASTER-Tavrida |   C |   180 | 19.2 |        
    3755 |         MASTER-SAAO | P\  |   180 | 17.3 |        
    3797 |      MASTER-Tavrida |   C |   180 | 19.5 |        
    3797 |      MASTER-Tavrida |   C |   180 | 19.2 |        
    3954 |         MASTER-SAAO | P\  |   180 | 15.7 |        
    3997 |      MASTER-Tavrida |   C |   180 | 19.8 |        
    3997 |      MASTER-Tavrida |   C |   180 | 19.4 |        
    4154 |         MASTER-SAAO | P\  |   180 | 16.4 |        
    4099 |          MASTER-IAC |   C |    60 | 17.6 |        
    4099 |          MASTER-IAC |   C |    60 | 17.3 |        
    4239 |          MASTER-IAC |   I |   180 | 16.9 |        
    4239 |          MASTER-IAC |   R |   180 | 17.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.


GRB_name: GRB210610B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30177
SUBJECT: GRB 210610B: BOOTES-2/TELMA optical observation
DATE:    21/06/10 21:25:06 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:

The 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) automatically responded to the Swift trigger of GRB 210610B (Page et al. GCNC 30170). Images were taken starting after the twilight as soon as it was possible. In the first co-added 7 x 10 s exposure image, we detect the reported optical afterglow with r = 17.5+-0.2 at 20:27 UT (~0.6 hr after trigger), also pinpointed by UVOT/Swift (Page et al. GCNC 30170), MASTER (Lipunov et al. GCNC 30173) and GIT (Kumar et al. GCNC 30174). Further observations are ongoing.

We thank the staff at La Mayora for its excellent support.


GRB_name: GRB210610B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30178
SUBJECT: GRB 210610B: CrAO/ZTSh optical afterglow photometry
DATE:    21/06/10 22:44:37 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

V. Rumyantsev (CrAO), A. Pozanenko (IKI),  S. Belkin (IKI), N. Pankov 
(HSE) report on behalf of GRB IKI FuN:

We report photometry of  GRB 210610B  afterglow (Page et al., GCN 
30170; Lipunov et al. GCNs 30173, 30176; Kumar et al. GCN 30174; 
Rumyantsev et al., GCN  30175; Hu et al., GCN 30177) obtained with ZTSh 
2.6m telescope of CrAO observatory.

Preliminary photometry of the optical afterglow in R- filter is following

Date       UT start    Filter Exp.   OT    Err.  UL(3sigma)
                               (s)

2021-06-10 20:19:24    R      1*10  16.11  0.02 21.5
2021-06-10 20:59:50    R      1*10  16.99  0.02 21.2

The photometry is based on the nearby USNO-A2.0 star
USNO-A2.0_id
1043-0282589 16:15:36.30 +14:23:18.2 R=16.88

We continue observations in BVRI filters and will report photometry 
after data receiving.


GRB_name: GRB210610B
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  30180
SUBJECT: GRB210610B: MeerLICHT multi-colour photometry
DATE:    21/06/10 22:52:22 GMT
FROM:    Paul Vreeswijk at Radboud U/Nijmegen  <p.vreeswijk@astro.ru.nl>

S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO), A.J. Levan and
P.M. Vreeswijk (Radboud) report on behalf of the MeerLICHT consortium:

"Following the detection of GRB210610B by Swift and its optical
counterpart (Page et al., GCN 30170), the 0.6m MeerLICHT telescope,
located at Sutherland, South Africa began observations of the field at
2021-06-10, 21:00:54 UT (1h9m after burst) with a repeating
sequence of optical filters: q,u,q,g,q,r,q,i,q,z, at 60s integration
time each. The q-band wavelength limits are 440-720nm.

First detections are:
q_AB = 17.25 +/- 0.01 +/- 0.02 at 21:00:54 UT
u_AB = 17.48 +/- 0.05 +/- 0.05 at 21:02:18 UT
g_AB = 17.39 +/- 0.02 +/- 0.03 at 21:05:27 UT
i_AB = 17.12 +/- 0.03 +/- 0.01 at 21:11:25 UT
z_AB = 17.10 +/- 0.07 +/- 0.02 at 21:14:26 UT
r_AB = 17.37 +/- 0.02 +/- 0.02 at 21:23:29 UT
where the first uncertainty on the magnitude is the statistical
uncertainty and the second is the uncertainty on the photometric
calibration. No correction for Galactic extinction has been made.

Inspection of DECaLS/DR3 data (Dey et al., 2019, AJ 157, 168) shows an
underlying blue galaxy, centered on RA,Dec (J2000) = 243.91823,
+14.39901, with magnitude g=22.97, r=22.87 and z=22.57. 

Further monitoring is continuing.

MeerLICHT is built and run by a consortium consisting of Radboud
University, University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester
and the University of Amsterdam."


