# GCN_circulars

GRB_name: GRB210205A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29398
SUBJECT: GRB 210205Aï¼š GWAC-F60A optical upper limit 
DATE:    21/02/05 11:50:51 GMT
FROM:    Liping Xin at NAOC, SVOM  <xlp@nao.cas.cn>

L. P. Xin(NAOC),  J. Wang(GXU), C. Gao(GXU), X. H. Han(NAOC), J. Y. Wei(NAOC), 
G. W. LI(NAOC),  L. H. Li(NAOC), C. Wu(NAOC),  X. G. Wang(GXU), 
E. W. Liang (GXU), R. S. Zhang(NAOC), Y. L. Qiu(NAOC), 
and J. S. Deng(NAOC) report: 

We began to observe GRB 210205A (Dichiaraet al., GCN 29397)
with Xinglong GWAC-F60A telescope, China, 
at 11:13:26 (UT), 5th. Feb. 2021, about 129 sec after the burst.

A series of  R, I, and B band images were obtained.
Preliminary analysis shows that no any new optical source
are found in single images within the XRT errorbox (Dichiaraet al., GCN 29397). 

The 3 sigma upper limit is about 17.3 mag in R band 
at the mean time of 134 sec after the burst,
calibrated to the USNO B1.0 catalog.


GRB_name: GRB210205A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29399
SUBJECT: GRB 210205A: Enhanced Swift-XRT position
DATE:    21/02/05 14:07:37 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 1148 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 210205A, 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 = 347.21907, +56.29649 which is equivalent
to:

RA (J2000): 23h 08m 52.58s
Dec (J2000): +56d 17' 47.4"

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: GRB210205A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29400
SUBJECT: GRB 210205A: BOOTES-4/MET optical upper limit
DATE:    21/02/05 15:11:13 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

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 210205A by Swift (Dichiara et al. GCNC 29397), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) started to gather images after the twilight as soon as it was possible. No new source is detected within the Swift/XRT enhanced position (Osborne et al. GCNC 29399) down to 18.3 mag in the co-added z-band images (7x120 s) starting at 12:22 UT. The non-detection is consistent with the limits reported by both Swift/UVOT (Dichiara et al. GCNC 29397) and GWAC-F60A (Xin et al. GCNC 29398).

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


GRB_name: GRB210205A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29401
SUBJECT: GRB 210205A: Nanshan/NEXT optical upper limit
DATE:    21/02/05 16:20:03 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210205A (Dichiara et al., GCN 29397) using 
the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained 
3x40 s, 4x60 s, 12x90 s frames in the Sloan r-band, starting at 12:09:46 
UT on 2021-02-05, i.e., 58.5 min after the BAT trigger.

No optical source is detected in our stacked image at the enhanced XRT 
position (Osborne et al., GCN 29399), down to a limiting magnitude of 
r~19.9, calibrated with the nearby PanSTARRS field.


GRB_name: GRB210205A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29402
SUBJECT: Swift GRB 210205A: Global MASTER-Net observations report 
DATE:    21/02/05 17:40:09 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-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) was pointed to the Swift GRB 210205A ( S. Dichiara et al., GCN 29397) errorbox  21040 sec after notice time and 21101 sec after trigger time at 2021-02-05 17:02:58 UT, with upper limit up to  17.4 mag. The observations began at zenith distance = 49 deg. The sun  altitude  is -22.7 deg. 

The galactic latitude b = -4 deg., longitude l = 109 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1540460

We obtain a following upper limits.  

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

   21191 |      MASTER-Tavrida |   C |   180 | 14.5 |        
   21191 |      MASTER-Tavrida |   C |   180 | 14.8 |        
   22639 |      MASTER-Tavrida |   C |   180 | 17.4 |        
   22639 |      MASTER-Tavrida |   C |   180 | 17.1 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210205A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29403
SUBJECT: GRB 210205A: Swift/UVOT Upper Limits
DATE:    21/02/05 18:16:08 GMT
FROM:    Alexander Belles at PSU/Swift  <aub1461@psu.edu>

A. Belles (PSU) and S. Dichiara (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210205A
139 s after the BAT trigger (Dichiara et al., GCN Circ. 29397).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 29399)
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           139          289          147         >20.5
white              139         4057          344         >20.6
v                 4268         4468          197         >19.4
b                 3652         5159          265         >20.1
u                  297         5084          255         >19.7
w1                4678         4878          197         >19.9
m2                4473         4673          197         >20.8
w2                4063         4263          197         >19.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.716 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210205B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29404
SUBJECT: GRB 210205B: AGILE/MCAL detection of a burst
DATE:    21/02/05 20:09:44 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), V. Fioretti (INAF/OAS-Bologna), 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, 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 Mini-CALorimeter (MCAL) detected a short burst at T0 = 2021-02-05
14:46:09.14 +/- 0.01 s (UTC).

The event lasted about 0.10 s and released a total number of ~94 counts in
the detector (in the 0.4-100 MeV energy range), above an average background
rate of 516 Hz, corresponding to a peak significance of ~8 sigma.

The MCAL light curve shows a single peak and can be found at
http://www.agilescienceapp.it/notices/071632_GRB_MCAL_539621169.143570.png .

The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the
energy range 0.4-100 MeV. 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: GRB210104A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29405
SUBJECT: ZTF21aagwbjr/AT2021buv: ZTF discovery of a fast optical transient likely associated with GRB 210104A
DATE:    21/02/05 20:10:12 GMT
FROM:    Erik Kool at Stockholm University  <erik.kool@astro.su.se>

Erik Kool (OKC), Igor Andreoni (Caltech), Anna Ho (UCB), Michael Coughlin (UMN), Tomas Ahumada (UMD), Yuhan Yao (Caltech), Daniel Perley (LJMU), Shreya Anand (Caltech), Mansi Kasliwal (Caltech) on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations.


We report the discovery of the fast optical transient ZTF21aagwbjr/AT2021buv with the Zwicky Transient Facility (ZTF, Bellm et al. 2019, Graham et al. 2019) at coordinates (J2000, <0.5):

RA = 07:48:19.32 (117.08054d)
Dec = +11:24:34.21 (+11.40949d)

ZTF21aagwbjr was first detected at r=17.11 mag on 2021-02-04 07:07 UT, hereafter labelled T_det, with an upper limit (g > 18.74 mag) 1.9 hours prior. It faded by ~2.1 mag in r-band in the next 0.9 days. The transient was most recently detected on 2021-02-05 06:07 UT at g = 19.70  0.07 mag. The color appears to be red, with g-r~0.4 on 2021-02-05. The Galactic extinction along the line of sight is low, with E(B-V)=0.04 mag (Planck Collaboration et al., 2015).

We note that ZTF21aagwbjr falls in the center of the error region of GRB210204A (GCN 29390), a long burst triggered by Fermi GBM 45 minutes before T_det. ZTF21aagwbjr is temporally and spatially consistent with GRB210204A (see https://zwicky.tf/j0s), and likely the afterglow.

In the table below, we report photometry obtained on images processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC (Masci et al. 2019).

-------------------------------------
Date (UT) | mag | emag | band
-------------------------------------
2021-02-04 05:14 | > 18.74 | - | g
2021-02-04 07:07 | 17.11 | 0.02 | r
2021-02-05 05:09 | 19.26 | 0.06 | r
2021-02-05 06:07 | 19.70 | 0.07 | g
-------------------------------------

ZTF21aagwbjr is located off the Galactic plane, with Galactic latitude b_Gal = 17.7 deg. A possible faint host is listed in the Legacy Survey DR9 catalog (Dey et al. 2019, ApJ, 157, 5), at RA, Dec = 07:48:19.32, 11:24:34.3, with a small separation of 0.1 arcsec from ZTF21aagwbjr. The source has a galaxy morphological classification, according to the DR9 Tractor model. The possible host has reported magnitudes of g=24.60, r=23.74, z=23.26, and a photometric redshift of 0.92  0.3.

We encourage spectroscopic classification and multi-wavelength follow-up of ZTF21aagwbjr, the likely afterglow of GRB210204A.


ZTF21aagwbjr was observed as part of the Caltech TESS shadowing survey (ATel #12952), and identified independently by two ZTF data mining programs: i) the ZTF Realtime Search and Triggering (ZTF-ReST) project, which aims at near real-time identification of compelling kilonova candidates in ZTF data using the methods described in Andreoni et al. (2020, ApJ, 904, 2), independently of gravitational-wave or gamma-ray triggers; ii) a filtering algorithm designed for fast transient discovery (Ho et al. 2020, ApJ, 905, 2).

ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done with Kowalski (Duev et al. 2019).


GRB_name: GRB210205A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29406
SUBJECT: GRB 210205A: MITSuME Ishigaki optical observation
DATE:    21/02/05 22:01:18 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 210205A (Dichiara et al., GCN 29397)
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
2021-02âˆ’05 11:22:29 UT (2 min after Swift BAT trigger).
We stacked the 25 images and did not find any new point sources
other than the USNO-B1.0 sources from the stacked images.
We obtained the SN = 10 limits as follows.

T0+[min] MID-UT T-EXP[sec] SN=10 limits
------------------------------------------------------------------------------------------------
2 2021-02-05T11:36:37 1500 g' > 18.7, Rc > 19.0, Ic > 17.8
------------------------------------------------------------------------------------------------


GRB_name: GRB210205A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29407
SUBJECT: GRB 210205A: Swift-XRT refined Analysis
DATE:    21/02/05 22:52:15 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), E. Ambrosi  (INAF-IASFPA) , M.
Capalbi (INAF-IASFPA), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto),
B. Sbarufatti (PSU) and S. Dichiara report on behalf of the Swift-XRT
team:

We have analysed 6.1 ks of XRT data for GRB 210205A (Dichiara et al.
GCN Circ. 29397), from 143 s to 28.3 ks after the  BAT trigger. The
data are entirely in Photon Counting (PC) mode. The enhanced XRT
position for this burst was given by Osborne et al. (GCN Circ. 29399).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.10 (+0.10, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.1 (+0.5, -0.4). The
best-fitting absorption column is  8.0 (+4.0, -2.8) x 10^21 cm^-2,
consistent with the Galactic value of 5.1 x 10^21 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 4.3 x 10^-11 (8.2 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      8.0 (+4.0, -2.8) x 10^21 cm^-2
Galactic foreground: 5.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      2.1 (+0.5, -0.4)

If the light curve continues to decay with a power-law decay index of
1.10, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.8 x
10^-14 (1.3 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/01030629.

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


GRB_name: GRB210204A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29408
SUBJECT: IPN triangulation of GRB 210204A
DATE:    21/02/05 23:27:45 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 long-duration GRB 210204A
(Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29390;
Bissaldi, GCN Circ. 29393;
BALROG localization: Kunzweileret al., GCN Circ. 29391;
GECAM detection: Li, GCN Circ. 29392)
has been detected by Fermi (GBM trigger 634112970), INTEGRAL (SPI-ACS),
Konus-Wind, Mars-Odyssey (HEND), and Swift (BAT), so far,
at about 23365 s UT (06:29:25).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, error box
whose coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   118.116 (07h 52m 28s) +15.249 (+15d 14' 57")
  Corners:
   120.374 (08h 01m 30s) +23.758 (+23d 45' 30")
   115.277 (07h 41m 07s)  +4.395 ( +4d 23' 43")
   114.946 (07h 39m 47s)  +4.455 ( +4d 27' 16")
   120.017 (08h 00m 04s) +23.825 (+23d 49' 30")
  ---------------------------------------------
The error box area is 6.7 sq. deg, and its maximum
dimension is 20.0 deg (the minimum one is 20 arcmin).
The Sun distance was 155 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. 29390 and 29391).

The optical transient ZTF21aagwbjr/AT2021buv (Kool et al., GCN Circ. 29405) 
is inside the box, lending support to the association of the transient and 
the burst.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/IPN/

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


GRB_name: GRB210205A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29409
SUBJECT: GRB 210205A: Swift-BAT refined analysis
DATE:    21/02/06 03:36:38 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
S. Dichiara (NASA/GSFC/UMCP), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), 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 210205A (trigger #1030629)
(Dichiara et al., GCN Circ. 29397).  The BAT ground-calculated position is
RA, Dec = 347.264, 56.311 deg which is
   RA(J2000)  =  23h 09m 03.3s
   Dec(J2000) = +56d 18' 41.2"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 18%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~ T-7 s and ends at ~T+20 s. The main peak in the structure
occurs at ~T+6 s. T90 (15-350 keV) is 22.70 +- 4.18 sec (estimated
error including systematics).

The time-averaged spectrum from T-7.35 to T+20.07 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 2.27 +- 0.31.  The fluence in the 15-150 keV band is
8.7 +- 1.6 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from
T+5.98 sec in the 15-150 keV band is 1.6 +- 0.5 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/1030629/BA/


GRB_name: GRB210204A
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29410
SUBJECT: GRB 210204A: AstroSat CZTI Detection
DATE:    21/02/06 10:46:42 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

G. Waratkar (IITB), V. Shenoy (IITB), A. Vibhute (IUCAA), S. Gupta 
(IUCAA), P. Sawant (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 bright long GRB 210204A, 
which was also detected by Fermi-GBM (GCN #29390, #29393) and GECAM-B 
(GCN #29392).

The source was clearly detected in the 20-200 keV energy range. The 
light curve showed two isolated emission peaks with the stronger peak at 
2021-02-04 06:32:45 UT in all four quadrants. The measured peak count 
rate associated with the burst is 789 (+58, -61) cts/s above the 
background in the combined data of four quadrants, with a total of 18141 
(+1631, -1364) cts. The initial fainter peak contributed to about 6% of 
the reported total counts. The local mean background count rate was 480 
(+2, -3) cts/s. Using cumulative rates, we measure a T90 of 200 (+7, 
-10) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector 
in the 100-500 keV energy range. The light curve showed two isolated 
peaks of emission with the stronger peak at 2021-02-04 06:32:45 UT. The 
initial fainter peak contributed less than 5% of total counts and hence 
was excluded from the following analysis. The measured peak count rate 
is 754 (+76, -80) cts/s above the background in the combined Veto data 
of four quadrants, with a total of 15971 (+827, -996) cts. The local 
mean background count rate was 1575 (+2, -3) cts/s. We measure a T90 of 
57 (+7, -5) 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. 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: GRB210204A
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29411
SUBJECT: VLT/X-shooter redshift of 1.466 for ZTF21aagwbjr/AT2021buv, strengthening its association with GRB 210204A
DATE:    21/02/06 11:15:41 GMT
FROM:    Maryam Arabsalmani at University of Melbourne  <mar.arabsalmani@gmail.com>

L. Izzo (DARK/NBI), J. P. U. Fynbo (DAWN/NBI), D. A. Kann (HETH/IAA-CSIC),
S. D. Vergani (GEPI, Observatoire de Paris), D. B. Malesani (DTU Space), M.
Arabsalmani (ICRAR/UWA), A. Rossi (INAF-OAS), G. Pugliese (API, Univ.
Amsterdam), D. Xu (NAOC), report on behalf of the Stargate consortium:

We observed the fast optical transient ZTF21aagwbjr/AT2021buv (Kool et al.,
GCN 29405), likely associated with the Fermi, GECAM, and IPN GRB 210204A
(The Fermi GBM team, GCN 29390; F. Kunzweiler et al., GCN 29391; Li et al.,
GCN 29392; Hurley et al., GCN 29408) using the ESO VLT UT3 (Melipal)
equipped with the X-shooter spectrograph. Spectroscopic observations
started at 01:38 UT on 06 February 2021, i.e. ~1.8 days after the burst
detection and they consisted of 4 x 600 s exposures. In the resulting
spectrum, we find a series of strong absorption lines that we identify as
Mg II, Si IV, C IV, and Ca II at a common redshift of 1.466. At this
redshift, we also detect emission lines of [O II], [O III] and H-alpha
Balmer line. We therefore conclude that z = 1.466 is the redshift of
ZTF21aagwbjr/AT2021buv.

The measured redshift implies a high intrinsic brightness (absolute
magnitude ~ 28 at an epoch of 45 min after the GRB; Kool et al., GCN
29405), which is typical of long GRB afterglows. This, coupled with the
observed absorption lines set, typical of long GRB environments, further
strengthens the association between ZTF21aagwbjr/AT2021buv and GRB 210204A.

Further analysis is undergoing.

We acknowledge support from the ESO observing staff at Paranal, in
particular Zahed Wahhaj.


GRB_name: GRB210204A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29412
SUBJECT: GRB 210204A: Swift ToO observations
DATE:    21/02/06 11:56:02 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 Fermi/GBM GRB 210204A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00014055

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 Fermi/GBM 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: GRB210204A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29413
SUBJECT: GRB 210204A / ZTF21aagwbjr: Swift-XRT observations
DATE:    21/02/06 16:22:25 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

Swift-XRT has performed follow-up observations of ZTF21aagwbjr (Kool et
al., 29405), which may be related to the Fermi/GBM / GECAM / IPN
detected burst GRB 210204A (GCN Circ., 29390, GCN Circ. 29392, GCN
Circ. 29408), collecting 2.9 ks of Photon Counting (PC) mode data
between T0+160.9 ks and T0+173.2 ks. 

An uncatalogued X-ray source is detected consistent with being within 1
arcsec of the ZTF position and is believed to be the afterglow, or at
least, the X-ray counterpart of the ZTF21aagwbjr. Using 2886 s of PC
mode data and 6 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 = 117.08071, +11.40951 which is equivalent to:
RA (J2000): 07h 48m 19.37s
Dec(J2000): +11d 24' 34.2"

with an uncertainty of 1.7 arcsec (radius, 90% confidence). This
position is 0.7 arcsec from the ZTF position.  The light curve is
consistent with a constant source of mean count rate 9.1e-02 ct/sec. 

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.73 (+0.31, -0.29). The
best-fitting absorption column is  1.7 (+1.3, -1.1) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 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 (4.9 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.7 (+1.3, -1.1) x 10^21 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 2.0 sigma
Photon index:      1.73 (+0.31, -0.29)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00014055. The results of the full
analysis of the XRT observations are available at
https://www.swift.ac.uk/ToO_GRBs/00014055.
This circular is an official product of the Swift-XRT team.


GRB_name: GRB210204A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29414
SUBJECT: GRB 210204A: Optical Observations from HCT
DATE:    21/02/07 04:46:24 GMT
FROM:    Anirban Dutta at Indian Inst. of Astrophysics  <anirban.dutta@iiap.res.in>

Teja, R.S.; Dutta, Anirban (IIA, Bengaluru); Kumar, Harsh (IIT, Bombay);
Sujith, D.S.; Sahu, D.K.; Anupama, G.C.; Barway, Sudhansu (IIA,
Bengaluru); Bhalerao, Varun (IIT, Bombay) 

We observed the field of GRB 210204A / ZTF21aagwbjr (Fermi-GBM, GCN
#29390; Li et al., GCN #29392; Izzo et al., GCN #29411) with the
Himalayan Faint Object Spectrograph and Camera (HFOSC) mounted on the
2-m Himalayan Chandra Telescope (IAO, Hanle, India). Multiple frames
(each 300 sec) of the GRB field in Bessell R and I bands were obtained
with an average airmass of 1.21 under good seeing conditions.
Preliminary PSF photometry on the stacked images was performed and
calibrated against USNO-B1 catalogue. We clearly detected an OT in the
stacked images in both the bands. The estimated magnitudes of the OT
(not corrected for the Galactic extinction) are as under - 

-------------------------------------------------------------------------------------
Date | UT (mean) | Filter | Exp. time x No. of frames | Magnitude (err)
-------------------------------------------------------------------------------------
2021-02-06 15:11:11    R             300 sec x 4                   20.07
(0.13)
2021-02-06 15:40:29    I              300 sec X 4                  19.79
(0.15)
-------------------------------------------------------------------------------------
The observations were carried out under the ToO program HCT-2021-C1-P2.
We thank the staff at IAO and CREST for helping us with the
observations.


GRB_name: GRB210204A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29415
SUBJECT: Konus-Wind detection of GRB 210204A / ZTF21aagwbjr
DATE:    21/02/07 14:27:40 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 210204A (Fermi GBM detection:  Bissaldi, GCN 29393;
GECAM detection: Li et al, GCN 29392;
IPN triangulation: Hurley et al., GCN 24908;
AstroSat CZTI Detection: Waratkar et al., GCN 29410),
associated with the fast optical transient ZTF21aagwbjr/AT2021buv
(Kool et al., GCN 29405),
triggered Konus-Wind (KW) at T0=23570.576 s UT (06:32:50.576).

The burst light shows a bright, multi-peaked pulse, which starts
at ~T0-30 s and has a duration of ~80 s.
A weaker precursor is clearly visible in the KW waiting
mode data around ~T0-165 s.
The emission in the main pulse is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/

As observed by Konus-Wind, the burst had
a fluence of (5.7 Â± 0.9)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+2.304,
of (5.0 Â± 0.7)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+49.408 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 (-0.12,+0.18),
the high energy photon index beta = -2.43 (-0.18,+0.31),
the peak energy Ep = 137 (-25,+22) keV,
chi2 = 79/97 dof.

The spectrum near the peak count rate (measured from T0
to T0+8.448 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 = -0.28 (-0.54,+0.64),
the high energy photon index beta = -2.12 (-0.24,+0.11),
the peak energy Ep = 123 (-24,+49) keV,
chi2 = 109/97 dof.

Assuming the redshift z=1.466 (Izzo et al., GCN 29411)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to ~2.3x10^53 erg,
the isotropic luminosity L_iso to ~7.1x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~340 keV.
With these values, GRB 210204A is within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., ApJ, in press),
see http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/GRB210204A_rest_frame.pdf



All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210207A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29416
SUBJECT: GRB 210207A: Fermi GBM Final Real-time Localization
DATE:    21/02/07 14:38:23 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 14:27:58 UT on 7 Feb 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210207A (trigger 634400883.983828 / 210207603).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 138.0, Dec = 4.7 (J2000 degrees, equivalent to J2000 09h 11m, 4d 42'), with a statistical uncertainty of 6.0 degrees.

The angle from the Fermi LAT boresight is 89.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210207603/quicklook/glg_skymap_all_bn210207603.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/bn210207603/quicklook/glg_healpix_all_bn210207603.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210207603/quicklook/glg_lc_medres34_bn210207603.gif


GRB_name: GRB210204A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29417
SUBJECT: GRB 210204A (ZTF21aagwbjr/AT2021buv): Mondy and AbAO optical observations
DATE:    21/02/07 16:34:13 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze 
(AbAO), N. Pankov (HSE) report  on behalf of GRB IKI FuN:

We observed the ZTF21aagwbjr/AT2021buv transient (Kool  et al., GCN 
29405) at  the redshift of 1.466 (Izzo et al., GCN 29411) which is most 
probably is an afterglow (Kennea et al., GCN 29413; Teja  et al., GCN 
29414) of  GRB 210204A (Fermi GBM team, GCN 29390; Li et al., GCN 29392; 
Hurley et al., GCN 29408; Waratkar et al., GCN 29410;  Frederiks et al., 
GCN 29415). Images in R-filter were taken in AZT-33IK telescope of Sayan 
observatory (Mondy) and AS-32 telescope of Abastumani observatory (AbAO).

Preliminary photometry of the optical transient in a combined image is 
following

Date       UT start  t-T0     Filter Exp.  OT    Err.  UL(3s) Telescope
                      (mid, days)        (s)

2021-02-06 12:33:10  2.26579  R      38*60 19.94 0.09  21.7  AZT-33IK
2021-02-06 16:50:17  2.44748  R      47*60 20.1  0.4   20.1  AS-32

The photometry is based on the nearby USNO-B1.0 stars.
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00


GRB_name: GRB210207A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29418
SUBJECT: GRB 210207A: BALROG localization (Fermi Trigger  / GRB 210207603)
DATE:    21/02/07 17:50:34 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
 at 14:27:58 on 07 Feb. 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) = 145.7+/-2.6 deg
Decl.(2000.0) = -1.4+/-2.6 deg
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB210207603/?data_version=h01

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/media/data/GRB210207603/data_files/210207_174515278495_GRB210207603_healpix_trigdat_h01.fits

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB210207603/json

                        


GRB_name: GRB210207A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29419
SUBJECT: Fermi GRB 210207A: Global MASTER-Net observations report 
DATE:    21/02/07 18:45:09 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-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) started inspect of the Fermi GRB 210207A ( Fermi GBM team, GCN 29416) errorbox  13574 sec after notice time and 13602 sec after trigger time at 2021-02-07 18:14:41 UT, with upper limit up to  19.0 mag. Observations started at twilight.  The observations began at zenith distance = 74 deg. The sun  altitude  is -8.5 deg. 

The galactic latitude b = 34 deg., longitude l = 227 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1541702

We obtain a following upper limits.  

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

   13632 | 2021-02-07 18:14:41 |         MASTER-SAAO | (09h 21m 17.86s , +03d 57m 57.2s) |   C |    60 | 14.1 |        
   13712 | 2021-02-07 18:16:01 |         MASTER-SAAO | (09h 09m 19.15s , +07d 57m 36.7s) |   C |    60 | 15.3 |        
   13891 | 2021-02-07 18:18:59 |         MASTER-SAAO | (09h 23m 02.39s , +05d 58m 05.0s) |   C |    60 | 14.8 |        
   14068 | 2021-02-07 18:21:56 |         MASTER-SAAO | (09h 04m 15.83s , +01d 58m 26.2s) |   C |    60 | 16.4 |        
   14147 | 2021-02-07 18:23:16 |         MASTER-SAAO | (09h 20m 16.34s , +01d 59m 51.9s) |   C |    60 | 16.1 |        
   14227 | 2021-02-07 18:24:36 |         MASTER-SAAO | (09h 20m 03.38s , -00d 01m 06.7s) |   C |    60 | 17.0 |        
   14307 | 2021-02-07 18:25:55 |         MASTER-SAAO | (09h 25m 24.18s , +07d 57m 54.8s) |   C |    60 | 15.8 |        
   14387 | 2021-02-07 18:27:15 |         MASTER-SAAO | (09h 05m 19.99s , +03d 57m 34.1s) |   C |    60 | 17.0 |        
   14466 | 2021-02-07 18:28:35 |         MASTER-SAAO | (09h 06m 56.83s , +05d 59m 03.6s) |   C |    60 | 17.0 |        
   14546 | 2021-02-07 18:29:55 |         MASTER-SAAO | (09h 21m 20.34s , +03d 57m 57.4s) |   C |    60 | 16.8 |        
   14626 | 2021-02-07 18:31:14 |         MASTER-SAAO | (09h 09m 19.98s , +07d 59m 20.3s) |   C |    60 | 17.4 |        
   14803 | 2021-02-07 18:34:11 |         MASTER-SAAO | (09h 22m 59.45s , +05d 59m 52.1s) |   C |    60 | 17.2 |        
   14980 | 2021-02-07 18:37:08 |         MASTER-SAAO | (09h 04m 15.52s , +01d 57m 23.0s) |   C |    60 | 18.2 |        
   15060 | 2021-02-07 18:38:28 |         MASTER-SAAO | (09h 20m 22.87s , +01d 57m 51.0s) |   C |    60 | 17.8 |        
   15139 | 2021-02-07 18:39:48 |         MASTER-SAAO | (09h 19m 59.64s , -00d 00m 23.3s) |   C |    60 | 19.0 |        
   15219 | 2021-02-07 18:41:07 |         MASTER-SAAO | (09h 25m 27.02s , +07d 58m 21.0s) |   C |    60 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210207B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29420
SUBJECT: GRB 210207B: Swift detection of a burst with a bright optical counterpart
DATE:    21/02/07 22:03:29 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

A. Y. Lien (GSFC/UMBC), E. Ambrosi (INAF-IASFPA),
S. D. Barthelmy (GSFC), A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC),
J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL),
S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), A. Tohuvavohu (U Toronto) and
E. Troja (NASA/GSFC/UMCP) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 21:52:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210207B (trigger=1031297).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 270.582, +53.694 which is 
   RA(J2000) = 18h 02m 20s
   Dec(J2000) = +53d 41' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 100 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~45 sec after the trigger. 

The XRT began observing the field at 21:53:22.0 UT, 73.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 270.6356, 53.6836 which is equivalent to:
   RA(J2000)  = 18h 02m 32.54s
   Dec(J2000) = +53d 41' 01.0"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 120 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 2.5 s image was 1.09e-08 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 82 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 18:02:32.40 = 270.63501
  DEC(J2000) = +53:40:56.0  =  53.68223
with a 90%-confidence error radius of about 0.74 arc sec. This position is 5.1
arc sec. from the center of the XRT error circle. The estimated magnitude is
13.72 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.041. 

Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov). 
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: GRB210207B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29421
SUBJECT: GRB 210207B: optical detection with 3.6m Devasthal Optical Telescope
DATE:    21/02/07 23:39:21 GMT
FROM:    Amit Kumar at ARIES, India  <amitkundu515@gmail.com>

 Amit Kumar (ARIES), Shashi B. Pandey (ARIES), Rahul Gupta (ARIES), Ankur
Ghosh (ARIES), Dimple  (ARIES), Amar Aryan (ARIES), Brajesh Kumar (ARIES),
and Kuntal Misra (ARIES) report:

We observed the Swift detected GRB 210207B (Lien et al., GCN 29420) using
the 4Kx4K CCD Imager (Pandey et al. 2018, 2018BSRSL..87...42P) mounted at
the axial port of the 3.6m Devasthal Optical Telescope (DOT) of ARIES
Nainital. The observations were carried out on 2021-02-07 in Bessel
UBVRI-bands starting from UT 22:32:31.875 (corresponding to 40.38 minutes
after the burst). We clearly detect the optical transient reported by Lien
et al., GCN 29420. In the first I band image the afterglow has a I band
magnitude of 15.61+/-0.01 mag. Further processing of the data is in
progress.

The quoted magnitude is calibrated with the nearby USNO-B1 stars and not
corrected for Galactic extinction in the direction of the GRB.
3.6m Devasthal Optical Telescope (DOT) is a recently commissioned facility
in the Northern Himalayan region of India (long:79 41 04E, lat:29 21 40N,
alt:2540m) owned and operated by the Aryabhatta Research Institute of
Observational Sciences (ARIES), Nainital (https://www.aries.res.in).
Authors of this GCN circular thankfully acknowledge consistent support from
the staff members to run and maintain the 3.6m DOT. This circular may be
cited.


GRB_name: GRB210207B
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29422
SUBJECT: GRB 210207B: Enhanced Swift-XRT position
DATE:    21/02/08 02:08:50 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 1993 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 210207B, 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 = 270.63474, +53.68210 which is equivalent
to:

RA (J2000): 18h 02m 32.34s
Dec (J2000): +53d 40' 55.5"

with an uncertainty of 1.7 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: GRB210207B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29423
SUBJECT: GRB 210207B: AbAO optical upper limit
DATE:    21/02/08 10:54:56 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), V. R. 
Ayvazian (AbAO),  G. V. Kapanadze (AbAO), N. Pankov (HSE, IKI)  report 
on behalf of IKI-GRB-FuN:

We observed the field of  GRB 210207B (Lien et al., GCN 29420) with 
AS-32 telescope of Abastumani observatory (AbAO) in R-filter starting on 
  2021-02-08 (UT) 02:14:17. The optical afterglow (Lien et al., GCN 
29420; Kumar et al., GCN 29421) is not detected in stacked image.

Date       UT start   t-T0    Filter  Exp.   OT    Err.  UL(3sigma)
                        (mid, days)     (s)


2021-02-08 02:14:17   0.19837  R      47*60   n/d  n/d   18.7


The photometry is based on nearby USNO-B1.0 stars
USNO-B1.0_id R2
1436-0267956 15.29
1436-0268040 15.52

The non-detection of the afterglow implies a jet break somewhere before 
of our observations, or the source of the  GRB 210207B is highly redshifted.


GRB_name: GRB210204A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29424
SUBJECT: Konus-Wind detection of GRB 210204A (correction to GCN 29415)
DATE:    21/02/08 11:35:19 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>

D. Frederiks, on behalf of the Konus-Wind team:

The KW spectral data and energetics of GRB 210204A
reported in Frederiks et al., GCN 29415 contain errors due to an
incorrect detector response matrix used in the calculations.
The correct spectra and energetics are provided below,
we are sorry for the inconvenience.

The burst time-integrated spectrum (measured from T0 to T0+49.408 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 = -1.45 (-0.08,+0.09),
the high energy photon index beta = -2.63 (-0.41,+0.20),
the peak energy Ep = 136 (-16,+21) keV,
chi2 = 76/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.448 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 = -1.12 (-0.18,+0.34),
the high energy photon index beta = -2.45 (-0.46,+0.26),
the peak energy Ep = 175 (-42,+34) keV,
chi2 = 104/96 dof.

As observed by Konus-Wind, the burst had
a fluence of (7.0 Â± 0.9)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+2.304,
of (5.2 Â± 0.9)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

Assuming the redshift z=1.466 (Izzo et al., GCN 29411)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to ~3.9x10^53 erg,
the isotropic luminosity L_iso to ~7.1x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~333 keV.
With these values, GRB 210204A is within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., ApJ, in press),
see http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/GRB210204A_rest_frame.pdf


All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210207B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29426
SUBJECT: Konus-Wind detection of GRB 210207B
DATE:    21/02/08 13:36:32 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 210207B (Swift detection:  Lien et al., GCN 29420)
triggered Konus-Wind (KW) at T0=78768.813 s UT (21:52:48.813).

The burst light shows a multi-peaked emission complex,
which starts at ~T0-50 s, peaks at ~T0, and has the total duration of ~110 s.
The emission in is seen up to ~2.5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210207_T78768/

As observed by Konus-Wind, the burst had
a fluence of (2.4 Â± 0.8)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+1.472,
of (4.5 Â± 0.8)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+65.792 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 = -0.85(-0.34,+0.44) and Ep = 334(-97,+237) keV (chi2 = 91/97 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 < -2.15
(chi2 =67/97 dof).

The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by the CPL model
with  alpha = -0.46(-0.22,+0.25) and Ep = 497(-84,+120) keV (chi2 = 76/97 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 < -2.33
(chi2 =76/96 dof).


All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.


GRB_name: GRB210207B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29427
SUBJECT: GRB 210207B: Swift-XRT refined Analysis
DATE:    21/02/08 13:40:11 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), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (PSU), D.N.
Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), P.A.
Evans (U. Leicester) and A.Y. Lien report on behalf of the Swift-XRT
team:

We have analysed 6.8 ks of XRT data for GRB 210207B (Lien et al. GCN
Circ. 29420), from 80 s to 45.6 ks after the  BAT trigger. The data
comprise 329 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN Circ. 29422).

The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.37 (+0.07, -0.06).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.99 (+/-0.04). The
best-fitting absorption column is  1.38 (+/-0.13) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.78 (+0.11, -0.10)
and a best-fitting absorption column of 7.2 (+2.9, -2.6) x 10^20 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      7.2 (+2.9, -2.6) x 10^20 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 2.3 sigma
Photon index:      1.78 (+0.11, -0.10)

If the light curve continues to decay with a power-law decay index of
1.37, the count rate at T+24 hours will be 0.021 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x
10^-13 (8.7 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/01031297.

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


GRB_name: GRB210207B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29428
SUBJECT: GRB 210207B: AGILE observations
DATE:    21/02/08 13:45:28 GMT
FROM:    Alessandro Ursi at INAF/IAPS  <alessandro.ursi@gmail.com>

A. Ursi (INAF/IAPS), F. Longo (Univ. Trieste and INFN Trieste), C. Pittori,
F. Verrecchia (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, 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 GRB 210207B, reported by Swift (GCNs #29420,
#29422, #29427) and Konus-Wind (GCN #29426) at T0 = 2021-02-07 21:52:08
(UT).

The AGILE Mini-CALorimeter (MCAL; 0.4-100 MeV) scientific ratemeters
clearly detected the main peak of the burst, which occurred at T0 + 40 s,
as reported by Swift/BAT. The episode lasted ~4 s and released 7950 counts
in the MCAL detector, above a background rate of 1250 Hz. The AGILE
ratemeters light curve can be found at:
http://www.agilescienceapp.it/notices/GRB210207B_AGILE_RM.png . The event
was 160Â° off-axis.

Additional analysis of AGILE data is in progress.


GRB_name: GRB210208A
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29429
SUBJECT: GRB 210208A: A long GRB detected by INTEGRAL
DATE:    21/02/08 14:22:35 GMT
FROM:    Sandro Mereghetti at IASF-Milano/INAF  <sandro.mereghetti@inaf.it>

S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno,
E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC,
Versoix)
and J.Borkowski (CAMK, Torun) report:

A gamma ray burst lasting about 3 s has been detected by IBAS in the
IBIS/ISGRI data at 13:32:23  UT of February 8, 2021.

The refined coordinates (J2000) are:
R.A.=  260.1976  deg
DEC.=  -12.6667 deg
with an uncertainty of 2 arcmin (90% c.l.).

The burst had a peak flux of about 0.9  counts/cm2/s (20-200 keV, 1-s
integration
time) and a fluence in the same energy range of about 2e-7  erg/cm2.

A plot of the light curve will  be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html


GRB_name: GRB210207B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29430
SUBJECT: GRB 210207B: KAIT Optical Observations
DATE:    21/02/08 16:12:38 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, responded to the Swift GRB 210207B (Lien et al.,

GCN 29420) starting at ~0.657 days after the trigger.

A total of 20x60s images were obtained in the clear (roughly R) filters.

We marginally detect the optical afterglow (Lien et al., GCN 29420;

Kumar et al., GCN 29421) in the coadd image with a mag of 20.3 +/- 0.3,

calibrated to the Pan-STARRS1 catalog.


GRB_name: GRB210207B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29431
SUBJECT: GRB 210207B: LCO Optical Afterglow Detection
DATE:    21/02/08 16:56:16 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 210207B (Lien, GCN 29420) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 8, from 11:23 to 11:34 UT (corresponding to 13.30 to 13.48 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 5x60s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent the initial UVOT detection (Lien, GCN 29420).  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 20.24 +/- 0.13

I = 20.56 +/- 0.24

These magnitudes are not corrected for galactic extinction.  A quick catalog search found no galaxies at this brightness at this location.  Further observations are encouraged.

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


GRB_name: GRB210204A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29432
SUBJECT: GRB 210204A: redshift revision of ZTF21aagwbjr/AT2021buv (correction to GCN 29411)
DATE:    21/02/08 18:20:17 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani@space.dtu.dk>

D. Xu (NAOC), L. Izzo (DARK/NBI), J. P. U. Fynbo (DAWN/NBI), D. A. Kann 
(HETH/IAA-CSIC), S. D. Vergani (GEPI, Observatoire de Paris), D. B. 
Malesani (DTU Space), M. Arabsalmani (ICRAR/UWA), A. Rossi (INAF-OAS), 
G. Pugliese (API, Univ. Amsterdam), J.-B. Vielfaure (APC), report on 
behalf of the Stargate consortium:

Off-line reanalysis of our data of GRB 210204A (ZTF21aagwbjr/AT2021buv; 
Kool et al., GCN 29405) made us realise that we had used an incorrect 
data set for our previous GCN circular (Izzo et al., GCN 29411). We 
report here the correct analysis and results, and urge users to 
disregard GCN 29411. We regret for any confusion created by this mishap.

Our data of GRB 210204A were acquired with the X-shooter spectrograph 
installed on the ESO VLT UT3 (Melipal) telescope. Four spectra by 600 s 
each were secured, starting on 2021 Feb 6.08 UT (1.79 days after the 
trigger) and covering the wavelength range 3000-21000 AA.

Continuum is clearly detected across the entire trace. A number of 
absorption features are detected; we identify, among others, Al II, Zn 
II, Fe II, Mg II, Mg I, Ca II H and K at a common redshift z = 0.876. In 
particular, fine-structure lines from Fe II* are also visible, which 
confirms the association of this absorption system with the GRB. 
Emission lines due to [O II], [O III], H beta and H alpha are also 
detected at z = 0.876.

We thus conclude that ZTF21aagwbjr/AT2021buv is at redshift z = 0.876.

Three intervening Mg II absorbers are also detected, at redshift 0.71, 
0.66, and 0.57.

The revision of the redshift value does not affect our previous 
conclusion that ZTF21aagwbjr/AT2021buv is the likely afterglow of GRB 
210204A (Fermi GBM Team, GCN 29390; Li et al., GCN 29392; Hurley et al., 
GCN 29408; Waratkar et al., GCN 29410): at z = 0.876, the transient 
reached an absolute magnitude of ~ -26.7 (Kool et al., GCN 29405), 
within the range of long GRB afterglows. The set of absorption features 
(including those due to fine-structure transitons) is also typical of 
GRB environments.

We recompute the isotropic-equivalent gamma-ray energy using the fluence 
reported by Konus-Wind (Frederiks, GCN 29424) and the correct redshift 
value, which turns to be ~8.7*10^52 erg.

We acknowledge the observing staff at Paranal, in particular Zahed Wahhaj.


GRB_name: GRB210204A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29433
SUBJECT: GRB 210204A: LBT observations and jet break
DATE:    21/02/08 19:23:12 GMT
FROM:    Andrea Rossi at INAF  <andrea.rossi@inaf.it>

A. Rossi (INAF-OAS Bologna), A. Melandri (INAF-OAB) report on behalf of 
the CIBO collaboration:

We observed the field of GRB210204A (Fermi GBM team, GCN 29390; Li et 
al., GCN 29392; Hurley et al., GCN 29408; Waratkar et al., GCN 29410; 
Frederiks et al., GCN 29415) simultaneously in the g'r'i' and z' bands 
with the LBC imager mounted on LBT  (Mt Graham, AZ, USA). We obtained 
20min of imaging for each band at the midtime 08:20 UT on 2021-02-07, 
3.08 days after the burst trigger.

We clearly detect the afterglow (Kool et al., GCN 29405) and we 
preliminary measure the following AB magnitudes:

g = 21.1 +- 0.1
r = 20.7 +- 0.1
i = 20.4 +- 0.1
z = 20.2 +- 0.1

calibrated against SDSS field stars.

Modelling the observations available (Kool et al., GCN29405 ; Belkin et 
al., GCN29417; Teja et al., GCN 29414) with a broken power-law, we find 
that the light curve first decays with index alpha_1=0.60+-0.05, then 
breaks at t_b=2.2+-0.2 days, and afterwards it is described by a decay
index alpha_2~1.7+-0.5. The last one is constrained only by the LBT 
detection, but is ~0.4 magnitude fainter than the brightness predicted 
extrapolating the pre-break decay.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly B. Rothberg, F. Cusano and D. Paris, in obtaining these 
observations.


GRB_name: GRB210207B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29434
SUBJECT: GRB 210207B: Insight-HXMT/HE detection
DATE:    21/02/09 01:22:58 GMT
FROM:    Chao Zheng at IHEP  <zhengchao97@ihep.ac.cn>

C. Zheng, C. Cai, J. C. Liu, Q. Luo, S. Xiao, 
W. C. Xue, Q. B. Yi, Y. Q. Zhang, Y. Huang, C. K. Li, 
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 2021-02-07T21:52:49.600 (T0), Insight-HXMT/HE detected 
GRB 210207B (trigger ID: HEB210207911) in a routine search of the data, 
which also triggered Swift/BAT (A. Y. Lien et al. , GCN #29420).

The Insight-HXMT/HE light curve mainly consists of a single 
pulse with a duration (T90) of 2.03 s measured from T0+0.24 s. 
The 1-ms peak rate, measured from T0+1.829 s, is 3687 cnts/sec. 
The total counts from this burst is 5247 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210207911_lc.jpg

All measurements above are made with the CsI detectors operating in the 
GRB mode with the energy range of about 250-3000 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: GRB210207B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29435
SUBJECT: GRB 210207B: Swift-BAT refined analysis
DATE:    21/02/09 01:29:50 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. Laha (GSFC/UMBC), 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-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210207B (trigger #1031297)
(Lien et al., GCN Circ. 29420).  The BAT ground-calculated position is
RA, Dec = 270.614, 53.700 deg which is
   RA(J2000)  =  18h 02m 27.3s
   Dec(J2000) = +53d 42' 01.1"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T0 and ends at ~T+106 s. The main peak occurs at ~T+43 s.
T90 (15-350 keV) is 95.69 +- 4.52 sec (estimated error including
systematics).

The time-averaged spectrum from T-0.25 to T+106.40 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.20 +- 0.07.  The fluence in the 15-150 keV band is 4.3 +- 0.2 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+43.16 sec in the 15-150 keV band
is 3.1 +- 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/1031297/BA/


GRB_name: GRB210207B
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29436
SUBJECT: GRB 210207B: Swift/UVOT Detection
DATE:    21/02/09 07:45:09 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210207B
82 s after the BAT trigger (Lien et al., GCN Circ. 29420).
A source consistent with the XRT position
(Lien et al. GCN Circ. 29420) is detected in the initial UVOT exposures,
as reported in the initial circular and confirmed by ARIES (Kumar et al.,
GCN Circ. 29421), KAIT (Zheng & Filippenko, GCN Circ. 29430) and LCO
(Strausbaugh & Cucchiara, GCN Circ. 29431). We note that the lack
of detection in the two bluer NUV passbands is suggestive of a redshift in
the 1.4-1.9 range.

The preliminary UVOT position is:
    RA  (J2000) =  18:02:32.40 = 270.63500 (deg.)
    Dec (J2000) = +53:40:55.8  =  53.68217 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections 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 (fc)          83          233          147      13.66+/-1.13
white             4081         5717          393      17.91+/-0.04
white            61938        62307          361      21.06+/-0.32
v                 4492         4692          196      17.61+/-0.10
v                 9433        10341          885      18.54+/-0.09
v                56912        74907         1297     >19.84
b                 3876         5512          393      17.95+/-0.05
b                44686        45593          885     >20.99
b                61025        79012         1770      20.79+/-0.18
u (fc)             295          410          113      14.42+/-0.03
u                 5106         5306          196      17.80+/-0.09
u                43773        44680          885      20.47+/-0.26
u                51795        69087          612     >19.80
uvw1              4901         5101          196      18.23+/-0.18
uvw1             11254        11428          171     >18.90
uvw1             39917        40544          616     >19.72
uvw1             50889        68646         1771     >20.53
uvm2              4697         4896          196     >19.12
uvm2             10346        11246          885     >20.23
uvw2              4287         5871          342     >19.39
uvw2             56005        74346         1771     >20.68

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.041 in the direction of the burst
(Schlegel et al. 1998).

[GCN OPS NOTE:  Per author's request the rerferece to Circ 294311
was changed to the correct value Circ 29431.]


GRB_name: GRB210207B
Detection_method: AstroSat CZTI
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29437
SUBJECT: GRB 210207B: AstroSat CZTI detection
DATE:    21/02/09 11:42:14 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

G. Waratkar (IITB), D. Nadella (NITK), V. Shenoy (IITB), A. Vibhute 
(IUCAA), S. Gupta (IUCAA), P. Sawant (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 bright long GRB 210207B, 
which was also detected by Swift (BAT - GCN #29420, #29435, XRT - 
#29422, #29427) Konus-Wind (GCN #29426), AGILE-MCAL (GCN #29428) and 
Insight-HXMT/HE (GCN #29434).

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 
2021-02-07 21:52:49 UT in all four quadrants. The measured peak count 
rate associated with the burst is 517 (+52, -57) cts/s above the 
background in the combined data of four quadrants, with a total of 3408 
(+384, -451) cts. The local mean background count rate was 560 (+3, -3) 
cts/s. Using cumulative rates, we measure a T90 of 42 (+10, -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 2021-02-07 21:52:48 UT. The 
measured peak count rate is 994 (+88, -93) cts/s above the background in 
the combined Veto data of four quadrants, with a total of 6364 (+849, 
-894) cts. The local mean background count rate was 1931.8 (+5, -5) 
cts/s. We measure a T90 of 44 (+9, -4) 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. 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: GRB210204A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29438
SUBJECT: GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Mondy optical observations
DATE:    21/02/09 12:40:35 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) 
report  on behalf of GRB IKI FuN:

We continued observation of the ZTF21aagwbjr/AT2021buv transient (Kool 
et al., GCN 29405) at the redshift of 0.876 (Xu et al., GCN 29432) which 
is  an afterglow (Kennea et al., GCN 29413; Teja  et al., GCN 29414) of 
  GRB 210204A (Fermi GBM team, GCN 29390; Li et al., GCN 29392; Hurley 
et al., GCN 29408; Waratkar et al., GCN 29410;  Frederiks et al., GCN 
29415). Images in R-filter were taken in AZT-33IK telescope of Sayan
observatory (Mondy) on Feb.7 and Feb.8.

Preliminary photometry of the optical transient in combined images in 
two epochs is following

Date       UT start  t-T0     Filter Exp.  OT    Err.  UL(3s) Telescope
                       (mid, days)        (s)

2021-02-07 13:43:58 3.32260  R      60*60 20.61 0.04  22.8  AZT-33IK
2021-02-08 15:22:01 4.39035  R      59*60 20.92 0.05  22.7  AZT-33IK

The photometry does not contradict a possible jet-break suggested by 
Rossi et al (GCN 29433).

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00


GRB_name: GRB210208A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29439
SUBJECT: GRB 210208A: BOOTES-2/TELMA optical upper limit
DATE:    21/02/09 14:56:47 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

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), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:

Following the detection of GRB 210208A by INTEGRAL (Mereghetti et al. GCNC 29429), the 60 cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) pointed to the position of the GRB, 17 deg away from the Galactic Center. No new source within the INTEGRAL/IBIS error box down to 17.3 mag is detected in the co-added image (2x60 s exposures, clear filter) obtained through a partially cloudy sky, at 06:17 UT on Feb 9 (~17.25 hr after trigger).

We thank the staff at La Mayora for their excellent support.


GRB_name: GRB210104A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29440
SUBJECT: GRB 210104A: LBT observations 
DATE:    21/02/09 15:09:31 GMT
FROM:    Andrea Melandri at INAF-OAB  <andrea.melandri@inaf.it>

A. Melandri (INAF-OAB), and A Rossi (INAF-OAS) report on behalf of the CIBO collaboration:

We observed the field of GRB 210104A (Troja et al., GCN 29233; Malacaria et al., GCN 29246) simultaneously in the r' and z' bands with the LBC imager mounted on LBT (Mt Graham, AZ, USA). We obtained 20min of imaging on 2021-02-05, 31.8 days after the burst trigger. Observations were performed under poor seeing (~1.7") conditions but reached a depth of r~25.5 mag.

At the position of the afterglow (Xin et al., GCN 29235; Hu et al., GCN 29236; Kim et al., GCNs 29238, 29265, 29283; Lipunov et al., GCNs 29239, 29248; Horiuchi et al., GCN 29241; Breeveld et al., GCN 29247; Paek et al., GCN 29254; Smartt et al., GCN 29262; Anandagoda et al., GCN 29273; Mao et al., GCN 29275; Moskvitin & Vlasyuk, GCN 29277; Belikin et al., GCN 29286; Nakamura et al., GCN 29291; Kann et al., GCN 29318), we clearly detect the host galaxy in both filters (RA,DEC = 06:55:05.18,+64:40:33.7; J2000).

After removing the halo of a nearby star, we measure the following AB magnitudes:

r = 24.2 +/- 0.3
z = 22.1 +/- 0.2

calibrated against SDSS field stars.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly B. Rothberg, F. Cusano, and D. Paris, in obtaining these observations.


GRB_name: GRB210207B
Detection_method: LCO
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29441
SUBJECT: GRB 210207B: Continued LCO Observations
DATE:    21/02/09 16:35:12 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 performed a second set of observations on Swift GRB 210207B (Lien, GCN 29420) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 9, from 11:19 to 11:24 UT (corresponding to 37.23 to 37.31 hours from the GRB trigger time) with the Bessel R filter.

We performed a second series of 4x60s exposures in R band. We no longer detect a source at the location consistent with other optical detections (Lien, GCN 29420; Kumar, GCN ; Zheng, GCN 29430; Strausbaugh, GCN 29431).  Using the USNO-B.1 catalog as reference, we calculate the following upper limit:

R > 21.42


These magnitudes are not corrected for galactic extinction.  This lack of a detection provides further evidence for the transient nature of this source.  As a correction to GCN 29431, the series of exposures in R and I bands were 4x60s, not the originally reported 5x60s.

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


GRB_name: GRB210209A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29442
SUBJECT: GRB 210209A: Swift detection of a burst
DATE:    21/02/09 21:51:50 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

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

At 21:39:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210209A (trigger=1031636).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 328.096, +43.559 which is 
   RA(J2000) = 21h 52m 23s
   Dec(J2000) = +43d 33' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 110 sec.  The peak count rate
was ~1600 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began observing the field at 21:41:41.0 UT, 116.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 328.12298, 43.55745 which
is equivalent to:
   RA(J2000)  = 21h 52m 29.52s
   Dec(J2000) = +43d 33' 26.8"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 70 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 3.98e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 126 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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
0.285. 

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: GRB210209A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29443
SUBJECT: GRB 210209A: Enhanced Swift-XRT position
DATE:    21/02/10 01:26:18 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 1987 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 210209A, 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 = 328.12225, +43.55698 which is equivalent
to:

RA (J2000): 21h 52m 29.34s
Dec (J2000): +43d 33' 25.1"

with an uncertainty of 1.5 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: GRB210210A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29444
SUBJECT: GRB 210210A: Swift detection of a burst with an optical counterpart
DATE:    21/02/10 02:27:51 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

S. Laha (GSFC/UMBC/CRESST), J.D. Gropp (PSU), H. A. Krimm (NSF),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (PSU) and A. Tohuvavohu (U Toronto)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 02:00:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210210A (trigger=1031728).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 262.811, +14.648 which is 
   RA(J2000) = 17h 31m 15s
   Dec(J2000) = +14d 38' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Due to a telemetry gap, only the first 
8 seconds of the BAT light curve after the trigger are available,
showing that the emission has at least two peaks and continues 
beyond that time.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 02:01:50.0 UT, 82.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 262.77059, 14.66385 which is equivalent
to:
   RA(J2000)  = 17h 31m 04.94s
   Dec(J2000) = +14d 39' 49.9"
with an uncertainty of 3.5 arcseconds (radius, 90% containment). This
location is 151 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 (8.82 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.2
(+1.27/-1.18) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 85 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
  RA(J2000)  = 17:31:05.00 = 262.77085
  DEC(J2000) = +14:39:45.8  =  14.66272
with a 90%-confidence error radius of about 1.10 arc sec. This position is 4.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.06. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.097. 

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: GRB210210A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29445
SUBJECT: Swift GRB 210210A: Global MASTER-Net observations report 
DATE:    21/02/10 02:38:25 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 210210A ( S. Laha et al., GCN 29444) errorbox  1609 sec after notice time and 1649 sec after trigger time at 2021-02-10 02:27:57 UT, with upper limit up to  16.5 mag. The observations began at zenith distance = 78 deg. The sun  altitude  is -20.7 deg. 

The galactic latitude b = 24 deg., longitude l = 38 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1544104

We obtain a following upper limits.  

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

    1739 |         MASTER-SAAO | P\  |   180 | 15.1 |        
    1939 |         MASTER-SAAO | P\  |   180 | 16.5 |        


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


GRB_name: GRB210210A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29447
SUBJECT: GRB 210210A: MASTER afterglow observation
DATE:    21/02/10 07:03:14 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER-SAAO robotic telescope (MASTER-Net: http://observ.pereplet.ru 
Lipunov et al.,2010,Advances in Astronomy,2010,30L)
automatically was pointed to Swift GRB 200210A (Laha et al. GCN 29444,Ttrigger 02:00:27UT)
at 2021-02-10 02:03:54UT (first exposition),
but the alert altitude was 07 degrees (under the roof, so there is no stars at first images)
and roses above the roof only 27min after trigger time  (Lipunov et al. GCN 29445).

MASTER auto-detection system found optical afterglow
  MASTER OT J173104.99+143945.9 (discovered by Swift-UVOT, GCN 29444).
We observed it untill sunrise (MASTER automatical programm of Swift alert observations).

The reduction of MASTER wide field and very wide field cameras images will be continued.
This message may be cited.


GRB_name: GRB210210A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29448
SUBJECT: GRB 210210A: Enhanced Swift-XRT position
DATE:    21/02/10 07:58:02 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 1221 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 210210A, 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 = 262.77041, +14.66257 which is equivalent
to:

RA (J2000): 17h 31m 4.90s
Dec (J2000): +14d 39' 45.2"

with an uncertainty of 1.7 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: GRB210209A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29449
SUBJECT: GRB 210209A: Swift-XRT refined Analysis
DATE:    21/02/10 08:13:33 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 6.3 ks of XRT data for GRB 210209A (Laha et al. GCN
Circ. 29442), from 122 s to 24.0 ks after the  BAT trigger. The data
comprise 139 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 29443).

The late-time light curve (from T0+4.3 ks) can be modelled with a
power-law decay with a decay index of alpha=0.88 (+/-0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.81 (+0.07, -0.04). The
best-fitting absorption column is  consistent with the Galactic value
of 3.7 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.91 (+0.07, -0.05) and a best-fitting absorption
column consistent with the Galactic value. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.0 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      3.67 (+0.14, -0.00) x 10^21 cm^-2
Galactic foreground: 3.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.91 (+0.07, -0.05)

If the light curve continues to decay with a power-law decay index of
0.88, the count rate at T+24 hours will be 0.046 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.9 x
10^-12 (2.6 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01031636.

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


GRB_name: GRB210210A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29450
SUBJECT: GRB 210210A: Redshift from OSIRIS/GTC
DATE:    21/02/10 11:24:24 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann, C. C. 
Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), and D. 
Garcia (GRANTECAN) report:

We observed the afterglow of GRB 210210A (Laha et al., GCN #29444, 
Lipunov et al., GCN #29447) with OSIRIS at the 10.4m Gran Telescopio 
Canarias (Roque de los Muchachos Observatory, La Palma, Canary Islands, 
Spain), starting at 2021-02-10 06:18:28.465 UT (4.300 hours after the 
trigger). The source is clearly detected. We obtained 3 x 900 s 
spectroscopy with the R1000B grism, covering the spectral range from 
3700 to 7800 AA.

 From the 30 s image starting at 2021-02-10 06:14:20.350 (0.1763 days 
after the trigger), we measure r' = 18.84 +/- 0.03 mag (AB) vs. a nearby 
PanSTARRS star. We note this indicates a slow decay compared with the 
initial Swift detection (Laha et al., GCN #29444). Further photometric 
follow-up is encouraged.

The spectrum shows a strong continuum over the full spectral range with 
several absorption lines. We identify these as FeII, MgII, and MgI, at a 
mean redshift of z = 0.715. At this redshift, we also detect OII in 
emission, which allows us to identify this as the redshift of the GRB. 
We also find an intervening system in MgII and MgI at z = 0.481.


GRB_name: GRB210208A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29451
SUBJECT: GRB 210208A: GIT optical upper limit
DATE:    21/02/10 11:38:40 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), S. Joharle(Fergusson College), J. Stanzin (IAO), V.
Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the
GIT team:

We observed GRB 210208A detected by INTEGRAL (S. Mereghetti et. al., GCN
#29429) with 0.7m GROWTH-India Telescope (GIT). We obtained four exposures
of 300-sec each in the r' filter. We did not detect any new source in our
stacked image within the 2 arcmin circle around R.A.= 260.1976 deg, DEC.=
-12.6667 deg. The obtained upper limit follows as:

-----------------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Exposure | Filter | Lim_mag (5-sigma) |

-----------------------------------------------------------------

 2459254.51368 | 10.78 | 300*4 (stacked) | r' | > 21.1 |

-----------------------------------------------------------------

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: GRB210210A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29452
SUBJECT: GRB 210210A: Swift-XRT refined Analysis
DATE:    21/02/10 14:06:05 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU),
J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.
Melandri (INAF-OAB) and S. Laha report on behalf of the Swift-XRT team:

We have analysed 7.7 ks of XRT data for GRB 210210A (Laha et al. GCN
Circ. 29444), from 85 s to 35.6 ks after the  BAT trigger. The data
comprise 58 s in Windowed Timing (WT) mode with the remainder in Photon
Counting (PC) mode. The enhanced XRT position for this burst was given
by Goad et al. (GCN Circ. 29448).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.27 (+/-0.07), followed by a break at T+1018 s to an
alpha of 1.06 (+0.45, -0.04).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.85 (+/-0.12). The
best-fitting absorption column is  1.3 (+0.4, -0.3) x 10^21 cm^-2, in
excess of the Galactic value of 8.8 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 3.7 x 10^-11 (4.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.3 (+0.4, -0.3) x 10^21 cm^-2
Galactic foreground: 8.8 x 10^20 cm^-2
Excess significance: 2.1 sigma
Photon index:      1.85 (+/-0.12)

If the light curve continues to decay with a power-law decay index of
1.06, the count rate at T+24 hours will be 0.021 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.9 x
10^-13 (9.7 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/01031728.

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


GRB_name: GRB210209A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29453
SUBJECT: GRB 210209A: Swift/UVOT Upper Limits
DATE:    21/02/10 14:39:45 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) 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 210209A 127 s after the BAT trigger 
(Laha et al., GCN Circ. 29442).
No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 29443) 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           127          276          147         >20.3
u_FC               285          535          246         >19.4
white              127          952          275         >20.4
v                  615         4730          236         >19.1
b                  540          733           39         >18.8
u                  285         5225          345         >19.8
w1                 664         5140          236         >19.7
m2                 639         4934          236         >19.4
w2                 590         4525          236         >20.5

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.286 in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB210209A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29455
SUBJECT: GRB 210209A: MITSuME Akeno optical upper limits
DATE:    21/02/10 14:59:37 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, R. Adachi, K. L. Murata, M. Niwano, F. Ogawa, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210209A (Laha et al. GCN #29442, Evans et
al. GCN #29443, Perri et al. GCN #29449, Breeveld et al. GCN #29453)
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
2021-02-10 08:49:41 UT(11.2 hour after the Swift BAT trigger). Since
the first 17 images were taken under high airmass conditions, we
stacked the images with good conditions. We did not find any new point
sources within the enhanced Swift XRT circle (Evans et al. GCN #29443)
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
------------------------------------------------------------------------------------------------
11.2 09:14:41 600 g'>17.2,Rc>17.6,Ic>17.1
------------------------------------------------------------------------------------------------
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: GRB210112A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29456
SUBJECT: GRB 210112A: LBT host detection and correction to GCN 29319 (CAHA observations)
DATE:    21/02/10 15:12:35 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

A. Rossi (INAF-OAS), on behalf of the CIBO collaboration, and D. A. Kann 
(HETH/IAA-CSIC) report:

We observed the field of GRB210112A (Ambrosi et al., GCN #29289; Ursi et 
al., GCN #29293; Svinkin et al., GCN #29315) simultaneously in the r' 
and z' bands with the LBC imager mounted on the Large Binocular 
Telescope (LBT, Mt. Graham, AZ, USA). We obtained 20 min of imaging on 
2021-02-05, 24.3 days after the burst trigger. Observations were 
performed under mediocre seeing conditions and reached a depth of r' ~ 
26 mag.

At the position of the afterglow (Ambrosi et al., GCN #29289), we 
clearly detect the host galaxy in both filters and we measure the 
following AB magnitudes:

r' = 23.96 +/- 0.15 mag,
z' = 23.38 +/- 0.15 mag.

calibrated against SDSS field stars.

Therefore, we confirm that the flattening observed by Kann et al. (GCN 
#29319) was due to the host component.

However, we do not see the faint object detected by Kann et al. at RA, 
Dec. = 14:36:01.453, +33:03:13.40 (J2000). We have investigated the CAHA 
and OSN (Kann et al., GCN 29296) images and found that the source 
detected by Kann et al., GCN 29319, which should have been "South" of 
the afterglow position, not "East", is the actual afterglow (with the 
fainter, northern extension possibly stemming from image distortion or a 
slight mismatch when co-adding frames), the offset stemming from a small 
arcsecond-scale astrometry mismatch. For the afterglow position, we 
measure Ic = 23.52 Â± 0.19 mag (AB), replacing the value given in GCN 
#29319. We estimate the underlying host to be Ic ~ 23.7 mag (AB) from 
the LBT photometry.

Correlating the OSN image with the LBT image, we find an afterglow 
position of RA, Dec. = 14:36:01.492 +33:03:14.945 (J2000), with errors 
of 0".2 in each coordinate, calibrated against Gaia DR2, in good 
agreement with the UVOT position (Ambrosi et al., GCN #29289).

In the LBT image, we furthermore detect a second, fainter, but probably 
also extended source just 2" north-north-east of the host (at RA, Dec. 
=14:36:01.54 +33:03:18.7; J2000) with r' = 24.5 Â± 0.2 mag. It is unclear 
if this likely galaxy is related to the host galaxy.

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly B. Rothberg and D. Paris, in obtaining these observations.


GRB_name: GRB210210A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29457
SUBJECT: GRB 210210A: Swift/UVOT Detection
DATE:    21/02/10 16:10:09 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) 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 210210A 85 s after the BAT trigger 
(Laha et al., GCN Circ. 29444). A fading source consistent with the XRT position
(Goad et al. GCN Circ. 29448) is detected in the initial UVOT exposures, as also detected by Lipunov 
et al. (GCN Circ. 29447) and de Ugarte Postigo et al. (GCN Circ. 29450).

The preliminary UVOT position is:
     RA  (J2000) =  17:31:05.01 = 262.77088 (deg.)
     Dec (J2000) = +14:39:46.4  =  14.66290 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections 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            85          235          147         16.04 Â± 0.03
white              878         1028          147         16.57 Â± 0.06
v                  629          648           20         16.95 Â± 0.19
b                  553          573           20         16.99 Â± 0.11
u                  298          547          246         15.91 Â± 0.03
w1                 679          699           19         16.05 Â± 0.15
m2                 827          847           19         16.13 Â± 0.20
w2                 779          798           20         16.35 Â± 0.18

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.097 in the direction of the burst (Schlegel et al. 1998).


GRB_name: GRB210209A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29458
SUBJECT: Swift GRB 210209A: Global MASTER-Net observations report 
DATE:    21/02/10 16:19:13 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-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) was pointed to the Swift GRB 210209A ( S. Laha et al., GCN 29442) errorbox  66257 sec after notice time and 66326 sec after trigger time at 2021-02-10 16:05:10 UT, with upper limit up to  17.5 mag. Observations started at twilight.  The observations began at zenith distance = 60 deg. The sun  altitude  is -11.3 deg. 

The galactic latitude b = -8 deg., longitude l = 92 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1543975

We obtain a following upper limits.  

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

   66416 |      MASTER-Tavrida |   C |   180 | 17.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210210A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29459
SUBJECT: GRB 210210A: LCO Optical Afterglow Detection
DATE:    21/02/10 16:24:44 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 210210A (Laha, GCN 29444) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on February 10, from 11:31 to 12:02 UT (corresponding to 9.52 to 10.04 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 5x180s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent the initial UVOT detection (Laha, GCN 29444).  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 19.62 +/- 0.05

I = 19.10 +/- 0.06

These magnitudes are not corrected for galactic extinction.

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


GRB_name: GRB210209A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29460
SUBJECT: GRB 210209A: BOOTES-4/MET optical upper limit
DATE:    21/02/10 16:29:26 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

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 210209A by Swift (Laha et al. GCNC 29442), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) started to gather images after the twilight as soon as it was possible. No new source is detected within the Swift/XRT enhanced position (Evans et al. GCNC 29443) down to 19.8 mag in the co-added images (15x60 s, clear filer) starting at 12:13 UT on Feb 10. The non-detection is consistent with the limits reported by both Swift/UVOT (Breeveld et al. GCNC 29453) and MITSuME (Hosokawa et al. GCNC 29455).

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


GRB_name: GRB210210B
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29462
SUBJECT: GRB 210210B: Fermi GBM Final Real-time Localization
DATE:    21/02/10 17:17:14 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 17:07:07 UT on 10 Feb 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210210B (trigger 634669632.657458 / 210210713).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 205.2, Dec = 17.3 (J2000 degrees, equivalent to J2000 13h 40m, 17d 18'), with a statistical uncertainty of 5.0 degrees.

The angle from the Fermi LAT boresight is 40.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210210713/quicklook/glg_skymap_all_bn210210713.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/bn210210713/quicklook/glg_healpix_all_bn210210713.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210210713/quicklook/glg_lc_medres34_bn210210713.gif


GRB_name: GRB210210B
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29465
SUBJECT: Fermi GRB 210210B: Global MASTER-Net observations report 
DATE:    21/02/10 21:30:29 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 210210B ( Fermi GBM team, GCN 29462) errorbox  13043 sec after notice time and 13073 sec after trigger time at 2021-02-10 20:45:00 UT, with upper limit up to  17.0 mag. The observations began at zenith distance = 67 deg. The sun  altitude  is -56.4 deg. 

The galactic latitude b = 74 deg., longitude l = 356 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1544564

We obtain a following upper limits.  

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

   13103 | 2021-02-10 20:45:00 |      MASTER-Tavrida | (13h 33m 22.67s , +20d 18m 01.2s) |   C |    60 | 12.4 |        
   13870 | 2021-02-10 20:57:47 |      MASTER-Tavrida | (13h 40m 24.21s , +18d 19m 54.4s) |   C |    60 | 13.2 |        
   13949 | 2021-02-10 20:59:06 |      MASTER-Tavrida | (13h 31m 46.86s , +16d 19m 09.2s) |   C |    60 | 12.0 |        
   14029 | 2021-02-10 21:00:26 |      MASTER-Tavrida | (13h 33m 15.74s , +20d 18m 13.4s) |   C |    60 | 17.0 |        
   14029 | 2021-02-10 21:00:26 |      MASTER-Tavrida | (13h 39m 37.50s , +20d 16m 21.3s) |   C |    60 | 13.7 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210210A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29467
SUBJECT: GRB 210210A: Swift-BAT refined analysis
DATE:    21/02/10 22:32:30 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),  H. A. Krimm (NSF),
S. Laha (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 210210A (trigger #1031728)
(Laha, et al., GCN Circ. 29444).  The BAT ground-calculated position is
RA, Dec = 262.764, 14.657 deg which is 
  RA(J2000)  =  17h 31m 03.4s 
  Dec(J2000) = +14d 39' 26.8" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The mask-weighted light curve shows a double-peaked structure running
approximately from T-1 sec to T+7 sec.  The first pulse peaks close to T+0 sec
and the second pulse peaks at T+4.5 sec.  T90 (15-350 keV) is 6.60 +- 0.59 sec 
(estimated error including systematics).

The time-averaged spectrum from T-0.75 to T+6.93 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.53 +- 0.58, 
and Epeak of 19.9 +- 13.9 keV (chi squared 44.33 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 9.8 +- 0.8 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+4.21 sec in the 15-150 keV band is
7.0 +- 0.5 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.46 +- 0.12 (chi squared 53.94 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/1031728/BA/


GRB_name: GRB210210A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29469
SUBJECT: GRB 210210A: FRAM-ORM afterglow detection
DATE:    21/02/11 07:35:59 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

Martin Jelinek and Jan Strobl (ASU CAS Ondrejov, CZ),
Sergey Karpov, Martin Masek, Petr Janecek, Jakub Jurysek, Jan Ebr, Ronan
Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague,
CZ)

report:

The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted robotically
to the alert of GRB210210A (Palmer et al GCNC 29444, Goad et al. GCNC
29448, D'Elia et al. GCNC 29452, and Lien et al GCNC 29467), obtaining a
set of 30 x 60 s R-band images starting at 03:37:09.2 UT, i.e. ~97min post
trigger.

We clearly detect the source reported by other telescopes (Lipunov et al.
GCN 29447, Fernandez-Garcia et al. GCNC 28763, de Ugarte Postigo et al GCNC
29450, Breeveld & Laha GCNC 29457, and Strausbaugh & Cucchiara GCNC 29459).
At the sum of all available images (Tmid=T0+113.2min) we measure the
optical afterglow with the brightness R=17.6+-0.2 (Vega) as calibrated
against the Atlas catalogue and Lupton transformations.


GRB_name: GRB210211A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29470
SUBJECT: GRB 210211A: Fermi GBM Final Real-time Localization
DATE:    21/02/11 08:50:50 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 08:43:18 UT on 11 Feb 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210211A (trigger 634725803.658592 / 210211363).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 283.8, Dec = -55.1 (J2000 degrees, equivalent to J2000 18h 55m, -55d 06'), with a statistical uncertainty of 11.8 degrees.

The angle from the Fermi LAT boresight is 45.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210211363/quicklook/glg_skymap_all_bn210211363.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/bn210211363/quicklook/glg_healpix_all_bn210211363.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210211363/quicklook/glg_lc_medres34_bn210211363.gif


GRB_name: GRB210211A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29472
SUBJECT: GRB 210211A: Swift detection of a burst
DATE:    21/02/11 09:00:56 GMT
FROM:    Phil Evans at U of Leicester  <pae9@star.le.ac.uk>

E. Troja (NASA/GSFC/UMCP), P. A. Evans (U Leicester),
H. A. Krimm (NSF), K. L. Page (U Leicester), B. Sbarufatti (PSU) and
M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 08:43:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210211A (trigger=1032024).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 269.433, -46.299 which is 
   RA(J2000) = 17h 57m 44s
   Dec(J2000) = -46d 17' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 10 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 08:44:32.2 UT, 73.9 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 269.4374, -46.2660
which is equivalent to:
   RA(J2000)  = 17h 57m 44.99s
   Dec(J2000) = -46d 15' 57.7"
with an uncertainty of 3.4 arcseconds (radius, 90% containment). This
location is 119 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 in excess of the Galactic value (1.24 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 8.7
(+9.04/-6.57) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 77 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. Because of the density of
catalogued stars, further analysis is required to report an upper limit for any
afterglow in the region. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.126. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
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: GRB210211A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29474
SUBJECT: GRB 210211A: REM optical/NIR afterglow detection
DATE:    21/02/11 11:19:34 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo, S. Covino, D. Fugazza, A. Melandri (INAF-OAB) on behalf of the REM team, report:

We observed the field of GRB 210211A (Troja et al., GCN Circ. 29472) with the REM 60cm robotic 
telescope located at the ESO premise of La Silla (Chile). The observations were performed starting 
on 2021 February 11 at 08:44:54 UT (i.e. 96 seconds after the burst) and were carried in the g, r, i, z, H 
bands simultaneously. 

From a preliminary analysis of the first set of images, obtained at a mid time of t-t0 = 101 s we detect in 
all filters an uncatalogued object at the following position: 

RA (J2000), Dec (J2000) = 17:57:45.67, -46:16:01.8 (+/- 0.5")

with a magnitude r = 16.9 +/- 0.1 (AB; calibrated against the APASS catalogue). This source is found about 
1.5 magnitudes fainter in a subsequent set of images obtained at t-t0 = 204 s. 

The source position lies about 8" outside the current available XRT error circle (https://www.swift.ac.uk/xrt_positions/). 
However, the observed brightness and rapid fading suggests that it is the optical/NIR afterglow of GRB 210211A. 
We also note the presence of an optical/NIR source inside the XRT error circle whose magnitude does not show significant 
variation in our dataset. 
 
Further analysis is in progress. 


GRB_name: GRB210210A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29476
SUBJECT: GRB 210210A: CAHA detection and likely jet break
DATE:    21/02/11 12:49:58 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), P. MÃ­nguez, and S. Pedraz (both CAHA) report:

We observed the afterglow (Laha et al., GCN #29444, Lipunov et al., GCN 
#29447, de Ugarte Postigo et al., GCN #29450, Breeveld & Laha, GCN 
#29457, Strausbaugh & Cucchiara, GCN #29459, Jelinek et al., GCN #29469) 
of the very soft GRB 210210A (Laha et al., GCN #29444) with CAFOS 
mounted on the 2.2m Calar Alto telescope (Almeria, Spain). We obtained 
one 180 s image each in BVRc and 3 x 90 s images in Ic. We detect the 
optical afterglow faintly in BVRc.

Using the same comparison star used by de Ugarte Postigo et al., and 
transforming to Rc following the equations of Lupton (2005), then 
transforming back to AB magnitudes, we derive:

Rc = 21.89 +/- 0.21 mag at 1.167362 days after the trigger.

Using the R-band magnitudes from the GCNs listed above (FRAM, Jelinek et 
al.; GTC, de Ugarte Postigo et al.; LCO, Strausbaugh & Cucchiara), we 
find an unbroken decay with alpha_1 = 1.05 until 0.41 days post-trigger. 
However, our detection lies 0.9 magnitudes below the extrapolation. 
Fixing the break time to 0.41 days, we find a lower limit on the 
post-break decay alpha_2 > 1.93. We note the X-ray afterglow also shows 
a potential jet break, with alpha_2 > 3, however, more observations are 
needed.


GRB_name: GRB210211A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29477
SUBJECT: GRB 210211A: MASTER optical observation of REM OT
DATE:    21/02/11 12:56:02 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin, V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)

MASTER-OAFA robotic telescope (MASTER-Net: http://observ.pereplet.ru Lipunov et al.,2010,Advances in Astronomy,2010,30L)
automatically started (Lipunov et al. GCN 29471)
Swift GRB 200211A (Troja et al. GCN 29472,Ttrigger=08:43:18UT)
at 2021-02-11 08:44:02UT with 10s exposition.
At the second (10s exp), third (20s exp) and fourth images we see OT,
discovered by REM (D'Avanzo et al. GCN29474)

The reduction of MASTER wide field and very wide field cameras images will be continued.
This message may be cited.


GRB_name: GRB210211A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29478
SUBJECT: GRB 210211A: Enhanced Swift-XRT position
DATE:    21/02/11 13:47:05 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 481 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210211A, 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 = 269.43976, -46.26729 which is equivalent
to:

RA (J2000): 17h 57m 45.54s
Dec (J2000): -46d 16' 02.3"

with an uncertainty of 2.4 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: GRB210209A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29479
SUBJECT: GRB 210209A: Swift-BAT refined analysis
DATE:    21/02/11 16:37:16 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),  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+800 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210209A (trigger #1031636)
(Laha, et al., GCN Circ. 29442).  The BAT ground-calculated position is
RA, Dec = 328.097, 43.545 deg which is 
  RA(J2000)  =  21h 52m 23.3s 
  Dec(J2000) = +43d 32' 40.4" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a  double-peaked structure running from
roughly T-35 sec to T+140 seconds.  The two peaks were at T+3 sec and T+65 sec.
T90 (15-350 keV) is 139.4 +- 21.5 sec (estimated error including systematics).

The time-averaged spectrum from T-40.34 to T+134.72 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.52 +- 0.12.  The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.68 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/1031636/BA/


GRB_name: GRB210210A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29481
SUBJECT: GRB 210210A as a BdHN II
DATE:    21/02/11 16:53:10 GMT
FROM:    Remo Rufinni at ICRA  <ruffini@icra.it>

R. Ruffini, R. Moradi, Y. Aimuratov, C. L. Bianco, M. Karlica,  J.A. Rueda,
N. Sahakyan, Y. Wang, Liang Li, S. S. Xue on behalf of the ICRANet team,
report:


GRB 210210A has T90=6.6s , observed by Swif-BAT (GCN 29467), with z=0.715
(GCN 29450), with an isotropic energy of E_iso ~ 2 x 10^51 erg, is the twin
of GRB 180728A ( Wang et al 2019 ApJ 874 39) with an  isotropic energy of
E_iso ~ 3 x 10^51 erg. It presents the typical characteristic of a subclass
of long GRBs called  Binary-driven Hypernovae of type II (BdHN II)
originating from a tight binary of a FeCO Core undergoing a supernova
explosion in presence of a companion neutron star (NS) which undergoes
hypercritical accretion.  The outcome (see Fig. [1]) is a new binary
composed by a more massive NS (MNS) and a newly born NS (*v*NS).


In both GRB 210210A and 180728A The GeV emission is not observed (GCN
29473); as it is expected in BdHN II. The follow-up observation in the
X-ray afterglow emission is recommended in order to determine the spin and
magnetic field of the new Neutron star (vNS) in this BdHN. We look forward
to possible data obtained from Fermi-GBM to recognize the supernovae rise
(SN-rise)(see Fig. [2]).

Using the averaged observed value (Cano et al., 2016), and considering the
redshift z=0.715 (A. Rossi et al., GCN 23055), a bright optical signal will
peak at 22 +/- 5 days after the trigger. However, the high redshift z=0.715
makes the observation challenging for this source.


Fig. 1: http://www.icranet.org/documents/SPHsimulation_CO-starSN-NS.pdf
Fig. 2:
http://www.icranet.org/documents/X-ray_afterglow_GRB180728A-GRB210210A.pdf


[GCN OPS NOTE: Per author's request, the last paragraph changes from:
"Using the averaged observed value (Cano et al., 2016), and considering the
redshift z=0.715 (A. Rossi et al., GCN 23055), a bright optical signal will
peak at 22 +/- 5 days after the trigger. However, the high redshift z=0.715
makes the observation challenging for this source."
to:
"Considering the red shift Z=0.715 (Ugarte et al, GCN 29450) a Supernova optical signal
will peak at 22 +/- 5 days after the trigger. However, the high redshift z=0.715,
makes the observation challenging for this source."
Removeing the Cano portion of the first sentence and correcting the Rossi citation
with the Ugarte citation.]


GRB_name: GRB210211A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29482
SUBJECT: GRB 210211A: Fermi GBM observation
DATE:    21/02/11 20:30:18 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC), A. von Kienlin (MPE), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 08:43:18.66 UT on 11 February 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210211A (trigger 634725803 / 210211363)
which was also detected by the Swift/BAT and Swift/XRT (E. Troja et al. 2021, GCN 29472).
The Fermi GBM Final Real-time Localization (GCN 29470) is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 50.5 degrees.

The GBM light curve shows multiple peaks
with a duration (T90) of about 29 s (50-300 keV).
The time-averaged spectrum from T0-4 s to T0+27 s is
best fit by a Band function with Epeak = 95 +/- 35 keV,
alpha = 2.8 +/- 3.1, and beta = -1.5 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(3.1 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.8 s in the 10-1000 keV band
is 1.8 +/- 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: GRB210211A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29483
SUBJECT: GRB 210211A: Swift-BAT refined analysis 
DATE:    21/02/11 20:52:22 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

C. B. Markwardt (GSFC), 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), E. Troja (NASA/GSFC/UMCP), 
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+600 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210211A (trigger #1032024)
(Troja, et al., GCN Circ. 29472).  The BAT ground-calculated position is
RA, Dec = 269.408, -46.270 deg which is 
  RA(J2000)  =  17h 57m 38.0s 
  Dec(J2000) = -46d 16' 11.0" 
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single broad peak starting at T-1 sec,
and decaying to background by T+8 sec.  T90 (15-350 keV) is 6.1 +- 0.6 sec 
(estimated error including systematics).

The time-averaged spectrum from T-0.70 to T+5.90 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.09 +- 0.16.  The fluence in the 15-150 keV band is 4.2 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+4.28 sec in the 15-150 keV band
is 1.0 +- 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/1032024/BA/


GRB_name: GRB210211A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29484
SUBJECT: GRB 210211A: Swift-XRT refined Analysis
DATE:    21/02/11 22:28:35 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto),
B. Sbarufatti (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 E. Troja report on behalf of the Swift-XRT
team:

We have analysed 9.6 ks of XRT data for GRB 210211A (Troja et al. GCN
Circ. 29472), from 81 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 Osborne et al. (GCN Circ. 29478).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.15 (+0.09, -0.08).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.5 (+0.7, -0.6). The
best-fitting absorption column is  6.7 (+6.5, -3.6) x 10^21 cm^-2, in
excess of the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.4 x 10^-11 (8.5 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      6.7 (+6.5, -3.6) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 2.5 sigma
Photon index:      2.5 (+0.7, -0.6)

If the light curve continues to decay with a power-law decay index of
1.15, the count rate at T+24 hours will be 7.2 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.4 x
10^-14 (6.1 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/01032024.

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


GRB_name: GRB210211A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29485
SUBJECT: GRB 210211A: Swift/UVOT Detection
DATE:    21/02/11 22:59:12 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210211A
78 s after the BAT trigger (Troja et al., GCN Circ. 29472). A source
consistent with the XRT position (Osborne et al. GCN Circ. 29478) and
the REM detection (d'Avanzo et al., GCN Circ. 29474)is detected in
the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  17:57:45.68 = 269.44035 (deg.)
    Dec (J2000) = -46:16:01.6  = -46.26711 (deg.)
with an estimated uncertainty of 0.47 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               78          227          147         17.89 +/- 0.06
white              596          611           15        >18.6
white             5391         5587          197        >20.3
v                 4239         4438          197        >19.8
b                  545          565           19        >18.4
u                  290          489          196        >18.6
m2                4444         4491           47        >18.3
w2                4034         4234          197        >19.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.127 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210207B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29486
SUBJECT: GRB 210207B: GECAM detection
DATE:    21/02/12 03:32:43 GMT
FROM:    Zhao Yi at POLAR  <yizhao@ihep.ac.cn>

Y. Zhao, X. Y. Song, S. Xiao, C. Cai, S. L. Xiong, Y. Huang, C. Y. Li,
J. J. He, Q. B. Yi, B. X. Zhang, Y. Q. Zhang, S. Y. Zhao, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, 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,
J. C. Liu, 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, W. C. Xue, S. Yang, M. Yao,
C. Y. Zhang,D. L. Zhang, Fan Zhang, Fei Zhang, H. M. Zhang, K. Zhang,
P. Zhang, S. N. Zhang, Z. Zhang, X. Y. Zhao, S. J. Zheng, X. Zhou (IHEP),
report on behalf of GECAM team:

During the commissioning phase, the ground search of GECAM-B data found
a long burst, GRB 210207B, at 2021-02-07T21:52:14.050 UTC (T0), which
was also reported by Swift/BAT (GCN #29420, #29435), Konus/Wind (GCN #29426),
AGILE (GCN #29428) and Insight-HXMT/HE (GCN #29434). 
The later bright pulse also triggered GECAM-B in-flight.

According to the GECAM-B light curves in about 8 keV-4 MeV, this burst
mainly consists of multiple pulses with a duration (T90) of 45.0 +/- 4.5 s
starting from T0 - 1.8 s. The 1-s peak counts rate is about 1300 cps
while the total counts is about 4600 counts.

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: 275.00 deg Dec: 51.57 deg
Err: 8.23 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 Swift (GCN #29420) within the error.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GECAM-B-tn210207_215215.pdf

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: GRB210212A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29487
SUBJECT: GRB 210212A: Swift detection of a burst
DATE:    21/02/12 04:50:37 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

E. Troja (NASA/GSFC/UMCP), J. A. Kennea (PSU), N. J. Klingler (PSU),
H. A. Krimm (NSF), F. E. Marshall (NASA/GSFC),
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 04:25:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210212A (trigger=1032183).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 72.261, +7.234 which is 
   RA(J2000) = 04h 49m 03s
   Dec(J2000) = +07d 14' 01"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a 
structure with a duration of about 50 sec.  The peak count rate
was ~1200 counts/sec (15-350 keV), at ~6 sec after the trigger. 

The XRT began observing the field at 04:27:00.9 UT, 103.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 72.2666,
7.2693 which is equivalent to:
   RA(J2000)  = 04h 49m 03.99s
   Dec(J2000) = +07d 16' 09.5"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 128 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. No spectrum from the promptly downlinked
event data is yet available to determine the column density. 

The initial flux in the 2.5 s image was 9.74e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
270 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 100% of the
XRT error circle. The typical 3-sigma upper limit has been about 19.2 mag. 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.094. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
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: GRB210210A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29488
SUBJECT: GRB 210210A : 1.3m DFOT optical observations
DATE:    21/02/12 10:22:31 GMT
FROM:    Dimple Panchal at ARIES, India  <dimplepanchal96@gmail.com>

Dimple (ARIES), A. Ghosh (ARIES), R. Gupta (ARIES), A. Kumar (ARIES), A.
Panchal (ARIES), K. Misra (ARIES), S.B. Pandey (ARIES), Y. C. Joshi (ARIES)
report:

We observed the afterglow (Laha et al. GCN #29444, Lipunov et al. GCN
#29447, de Ugarte Postigo et al. GCN #29450, Breeveld & Laha, GCN
#29457, Strausbaugh & Cucchiara, GCN #29459, Jelinek et al. GCN
#29469,  D. A. Kann et al. GCN #29476) of the GRB 210210A (Laha et al.
GCN #29444) with 1.3m Devasthal Fast Optical Telescope (DFOT) at
Devasthal observatory of Aryabhatta Research Institute of
observational sciencES (ARIES), India. We obtained multiple images in
R and I bands with an exposure of 180 seconds each. We detect the
optical afterglow with a magnitude of 21.35 +- 0.07 in R-band at 0.88
days after the burst. Further observations are ongoing with 1.3m DFOT
and 3.6m DOT.

The magnitude is not corrected for the Galactic extinction in the
direction of the burst. The photometric calibration is performed using
the standard stars from the USNO-B1.0 catalog.


GRB_name: GRB210212A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29489
SUBJECT: GRB 210212A: Enhanced Swift-XRT position
DATE:    21/02/12 10:44:09 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 478 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210212A, 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 = 72.26662, +7.26968 which is equivalent
to:

RA (J2000): 04h 49m 3.99s
Dec (J2000): +07d 16' 10.8"

with an uncertainty of 3.7 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: GRB210204A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29490
SUBJECT: GRB 210204A: observations with the 3.6m Devasthal Optical Telescope and possible jet break
DATE:    21/02/12 12:06:31 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

R. Gupta, S. B. Pandey, A. Kumar, Dimple, A. Ghosh, A. Aryan, K. Misra
(ARIES), D. Bhattacharya (IUCAA), V. Bhalerao (IITB), A. Pozanenko (IKI),
and D. Buckley (SAAO) as a part of larger BRICS collaboration:

GRB 210204A was triggered by the Fermi-GBM at 06:29:25 UT on 4 Feb 2021
(GCNs 29390, and 29393) and the prompt emission was also detected by other
space-based facilities like GECAM (29392), AstroSat (GCN 29410), and
Konus-Wind (GCNC 29415) up to MeV energies.  So, we searched for extended
GeV emission for a temporal window of 50 ks since GBM trigger-based on
available LAT data, however,  we do not find detection of any GeV photons
with a probability greater than 50 % to be associated with the source.

The optical counterpart associated with this burst was independently
discovered by Kool et al., 2021 using the ZTF telescope (GCN 29405) and
later follow-up observations were continued by several ground-based
facilities (GCNs 29411, 29414, 29417, 29432, 29433, and 29438). Xu et al.
2021 report a redshift value of 0.876 for this burst using
VLT/X-shooter observations
(GCN 29411).

We performed late time follow-up observations of the optical counterpart
using the 4Kx4K CCD Imager (Pandey et al. 2017, arXiv:1711.05422v1) mounted
at the axial port of the 3.6m Devasthal Optical Telescope of ARIES Nainital
starting ~ 58 hours after the burst. Multiple frames were taken in various
broad-band filters including B, V, R, and I bands. A fading afterglow
candidate was clearly seen in individual frames decayed around ~ 0.6 mags
in R Band during our observing run. We report the preliminary brightness of
the afterglow to be R= 20.19 +/- 0.03 mag ~ 58 hours after the GBM trigger.
The magnitude value reported is calibrated against UNSO B1 nearby stars.
Our R-band light curve along with early data published by Kool et al., 2021
(GCN 29405) is well-described with a broken power-law model. We found that
the temporal decay index before break time (~ 36 hours post burst) is 0.55
+/- 0.03 steepen to 1.43 +/- 0.09 at later epochs. Considering this break
as a jet break (as reported in GCN 29433), we calculated the optical
spectral index (using BVRI data at ~ 58 hours) \beta_O to be 1.08 +/- 0.10.
Considering the closure relations after the jet break (both for ISM and
WIND like a medium, without energy injection), the optical emission could
be better described with spectral regime \nu > \nu_c for WIND medium
demanding electron energy index value $p$ equal to 2.16 +/- 0.20 for the
available data-set so far.

This circular maybe cited. 3.6m Devasthal Optical Telescope (DOT) is a
recently commissioned facility in the Northern Himalayan region of India
(long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the
Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital (
https://www.aries.res.in). Authors of this GCN circular thankfully
acknowledge consistent support from the staff members to run and maintain
the 3.6m DOT.


GRB_name: GRB210212A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29491
SUBJECT: GRB 210212A: Swift-BAT refined analysis
DATE:    21/02/12 14:38:20 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

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

Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210212A (trigger #1032183)
(Troja, et al., GCN Circ. 29487).  The BAT ground-calculated position is
RA, Dec = 72.249, 7.215 deg which is 
  RA(J2000)  =  04h 48m 59.7s 
  Dec(J2000) = +07d 12' 52.6" 
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve showed a broad peak with some underlying
structure.  It began around T-10 sec, peaked around T+5 sec and returned to
background by T+90 sec.  T90 (15-350 keV) is 80.0 +- 35.8 sec (estimated 
error including systematics).

The time-averaged spectrum from T-15.51 to T+80.49 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.85 +- 0.23.  The fluence in the 15-150 keV band is 8.0 +- 1.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+7.99 sec in the 15-150 keV band
is 0.5 +- 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/1032183/BA/


GRB_name: GRB210212A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29492
SUBJECT: GRB 210212A: Swift/UVOT Upper Limits
DATE:    21/02/12 14:53:24 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210212A
112 s after the BAT trigger (Troja et al., GCN Circ. 29487).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 29489)
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           112          262          147         >20.6
u_FC               271          520          246         >20.3
white              112          930          242         >20.8
v                  600         4588          236         >19.0
b                  526          720           39         >19.3
u                  271          868          285         >20.4
w1                 650         4851           90         >19.1
m2                 626         4793          235         >19.7
w2                  93         4383          245         >19.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.094 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210212A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29494
SUBJECT: GRB 210212A: BOOTES-4/MET optical upper limit
DATE:    21/02/12 15:40:39 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

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 210212A by Swift (Troja et al. GCNC 29487), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) started to gather images after the twilight as soon as it was possible. No new source is detected within the Swift/XRT enhanced position (Beardmore et al. GCNC 29489) down to 19.7 mag in the co-added images (5x60 s, clear filer) starting at 13:11 UT on Feb 12. The non-detection is consistent with the limit reported by Swift/UVOT (Troja et al. GCNC 29487).

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


GRB_name: GRB210212A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29495
SUBJECT: GRB 210212A: Swift-XRT refined Analysis
DATE:    21/02/12 16:18:16 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU),
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo
(INAF-OAB) and E. Troja report on behalf of the Swift-XRT team:

We have analysed 6.8 ks of XRT data for GRB 210212A (Troja et al. GCN
Circ. 29487), from 109 s to 34.2 ks after the  BAT trigger. The data
comprise 337 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Beardmore et al. (GCN Circ. 29489).

The light curve can be modelled with an initial power-law decay with an
index of alpha=2.27 (+0.28, -0.50), followed by a break at T+194 s to
an alpha of 3.79 (+0.28, -0.23).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.55 (+0.13, -0.12). The
best-fitting absorption column is  1.6 (+0.6, -0.4) x 10^21 cm^-2,
consistent with the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum  is 4.4 x 10^-11 (5.0 x
10^-11) erg cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Total column:      1.6 (+0.6, -0.4) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.55 (+0.13, -0.12)

If the light curve continues to decay with a power-law decay index of
3.79, the count rate at T+24 hours will be 5.3 x 10^-10 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x
10^-20 (2.6 x 10^-20) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01032183.

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


GRB_name: GRB210212A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29496
SUBJECT: GRB 210212A: MITSuME Akeno optical upper limits
DATE:    21/02/12 16:58:03 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

K. L. Murata, R. Adachi, R. Hosokawa, M. Niwano, F. Ogawa, N. Nakamura, N.
Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai (TokyoTech)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 210212A (Troja et al. GCN #29487, Beardmore et
al. GCN #29489, Palmer et al. GCN #29491, Kuin et al. GCN #29492, Hu et al.
GCN #29494, Tohuvavohu et al. GCN #29495)  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 2021-02-12 08:51:45 UT(4.43 hours after the Swift
BAT trigger). We stacked the images with good conditions. We did not find
any new point sources within the enhanced Swift XRT circle (Beardmore et
al. GCN #29489) 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
------------------------------------------------------------------------------------------------
8.6 13:05:08 5400 g'>18.6, Rc>18.5, Ic>17.8
------------------------------------------------------------------------------------------------
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: GRB210212A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29497
SUBJECT: Swift GRB 210212A: Global MASTER-Net observations report 
DATE:    21/02/12 19:28:27 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-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 210212A ( E. Troja et al., GCN 29487) errorbox  53602 sec after notice time and 53674 sec after trigger time at 2021-02-12 19:19:52 UT, with upper limit up to  18.1 mag. The observations began at zenith distance = 44 deg. The sun  altitude  is -21.6 deg. 

The galactic latitude b = -22 deg., longitude l = 191 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1545497

We obtain a following upper limits.  

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

   53764 |         MASTER-SAAO |   C |   180 | 18.1 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210212A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29498
SUBJECT: GRB 210212A: Possible host galaxy counterpart with the NOT
DATE:    21/02/12 22:31:32 GMT
FROM:    Kasper Elm Heintz at Univ. of Iceland and DAWN/NBI  <keh14@hi.is>

K. E. Heintz (Univ. of Iceland), D. B. Malesani (DTU space), L. Izzo (DARK/NBI), and A. A. Djupvik (NOT), report on behalf of a larger collaboration:

We observed the field of GRB 210212A (Troja et al., GCN #29487), using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Starting at 20:05:37 UTC on February 12, i.e. 15.5 hr after trigger, we obtained 3x600s exposures in the r-band. The observations were carried out under good conditions, with seeing around 0.8".

Within the refined Swift/XRT error circle (Beardmore et al., GCN #29489), we detect a faint, extended source with FWHM = 1.5". We measure r = 23.23 +/- 0.12 mag, calibrated against nearby field stars in the Pan-STARRS DR1 catalog. At the same position, we also tentatively detect a source in archival Pan-STARRS images.

This source is potentially the host galaxy of GRB 210212A. However, due to the relatively large uncertainty of the currently available XRT position (3.6"), we estimate a chance probability for this source to be unrelated to the GRB of P = 0.09 based on the formalism by Bloom et al. (2002, AJ, 123, 1111). 


GRB_name: GRB210204A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29499
SUBJECT: GRB 210204A (ZTF21aagwbjr/AT2021buv): continued CrAO and AbAO optical observations
DATE:    21/02/12 23:18:51 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), V. Rumyantsev (CrAO), R. Ya. 
Inasaridze (AbAO), N. Pankov (HSE) report on behalf of GRB IKI FuN:

We continued observation of the ZTF21aagwbjr/AT2021buv transient (Kool 
et al., GCN 29405) at the redshift of 0.876 (Xu et al., GCN 29432) which 
is  an afterglow (Kennea et al., GCN 29413; Teja  et al., GCN 29414; 
Belkin  et al., GCNs 29417, 29438;   Rossi et al., GCN 29433; Gupta et 
al., GCN 29490) of  GRB 210204A (Fermi GBM team, GCN 29390; Li et al., 
GCN 29392; Hurley et al., GCN 29408; Waratkar et al., GCN 29410; 
Frederiks et al., GCN 29415). Images in R-filter were taken with AS-32 
telescope of Abastumani observatory (AbAO) and  ZTSh 2.6m telescope of 
CrAO observatory on 2021-02-09 and 2021-02-11.

Preliminary photometry of the afterglow in combined images is following

Date       UT start  t-T0     Filter Exp.  OT    Err.  UL(3s) Telescope
                       (mid, days)        (s)

2021-02-09 18:41:28 5.52572  R      25*120 21.09 0.08  22.6  ZTSh
2021-02-09 19:28:42 5.55610  R      43*60  21.4  0.2   22.5  AS-32
2021-02-11 18:18:20 7.50966  R      50*60  21.8  0.2   22.5  AS-32
2021-02-11 21:32:47 7.64817  R      30*120 21.6  0.3   21.8  ZTSh

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00

A light curve can be found in
http://grb.rssi.ru/GRB210204A/GRB210204A_lc.png

Our photometry confirms suggested jet-break (Rossi et al. GCN 29433; 
Gupta et al., GCN 29490).


GRB_name: GRB210210A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29502
SUBJECT: GRB 210210A: CAHA 2nd epoch and jet break confirmation
DATE:    21/02/13 11:21:45 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), P. Minguez, and S. Pedraz (both CAHA) report:

We again observed the afterglow (Laha et al., GCN #29444, Lipunov et 
al., GCN #29447, de Ugarte Postigo et al., GCN #29450, Breeveld & Laha, 
GCN #29457, Strausbaugh & Cucchiara, GCN #29459, Jelinek et al., GCN 
#29469, Kann et al., GCN #29476, Dimple et al., GCN #2948 of GRB 210210A 
(Laha et al., GCN #29444) with CAFOS mounted on the 2.2m Calar Alto 
telescope (Almeria, Spain). We obtained 6 x 600 s image in Rc. We detect 
the optical afterglow faintly in the stacked Rc image.

Using the same comparison star used by de Ugarte Postigo et al., and 
transforming to Rc following the equations of Lupton (2005), then 
transforming back to AB magnitudes, we derive a preliminary magnitude:

Rc = 23.05 +/- 0.14 mag at 3.129261 days after the trigger.

Using the R-band magnitudes from the GCNs listed above, now also 
including Dimple et al., GCN #29488, we confirm the steeper decay found 
by Kann et al., GCN #29476, finding, with a host-galaxy magnitude as a 
free parameter:

alpha_1 = 1.06 +/- 0.18,
alpha_1 = 2.50 +/- 0.90,
t_b = 0.45 +/- 0.23 days,
m_h = 23.19 +/- 0.27 mag (AB).

This fit can be improved with a dedicated host-galaxy observation. We 
note that the X-ray light curve also shows evidence for a possible jet 
break at 0.35 +0.27 -0.13 days, in agreement with our result.


GRB_name: GRB210213A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29503
SUBJECT: GRB 210213A: Fermi GBM Final Real-time Localization
DATE:    21/02/13 17:57:36 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 17:47:14 UT on 13 Feb 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210213A (trigger 634931239.164872 / 210213741).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 122.5, Dec = 22.2 (J2000 degrees, equivalent to J2000 08h 09m, 22d 11'), with a statistical uncertainty of 4.3 degrees.

The angle from the Fermi LAT boresight is 100.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210213741/quicklook/glg_skymap_all_bn210213741.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/bn210213741/quicklook/glg_healpix_all_bn210213741.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210213741/quicklook/glg_lc_medres34_bn210213741.gif


GRB_name: GRB210213A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29505
SUBJECT: Fermi GRB 210213A: Global MASTER-Net observations report 
DATE:    21/02/13 19:15:07 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) started inspect of the Fermi GRB 210213A ( Fermi GBM team, GCN 29503) errorbox  2736 sec after notice time and 2763 sec after trigger time at 2021-02-13 18:33:17 UT, with upper limit up to  18.9 mag. Observations started at twilight.  The observations began at zenith distance = 65 deg. The sun  altitude  is -13.2 deg. 

The galactic latitude b = 27 deg., longitude l = 201 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1546624

We obtain a following upper limits.  

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

    2793 | 2021-02-13 18:33:17 |         MASTER-SAAO | (07h 59m 18.94s , +21d 55m 15.3s) |   C |    60 | 18.6 |        
    2873 | 2021-02-13 18:34:37 |         MASTER-SAAO | (08h 06m 26.34s , +23d 55m 29.8s) |   C |    60 | 18.3 |        
    2972 | 2021-02-13 18:36:16 |         MASTER-SAAO | (08h 16m 14.99s , +21d 56m 55.8s) |   C |    60 | 18.9 |        
    3072 | 2021-02-13 18:37:55 |         MASTER-SAAO | (08h 10m 06.28s , +19d 56m 24.2s) |   C |    60 | 17.8 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210212A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29507
SUBJECT: GRB 210212A: Gemini South optical observations
DATE:    21/02/13 21:55:21 GMT
FROM:    Simone Dichiara at UMCP/NASA/GSFC  <dichiara@umd.edu>

S.Dichiara (UMD, NASA-GSFC) and E. Troja (UMD, NASA-GSFC) report:

We observed the field of GRB 210212A (Troja et al., GCN Circ. 29487) with
the Gemini South telescope beginning 2021-02-13 02:16:45  UT, approximately
0.91 days post-burst. We obtained 9x120 s exposures in r-band performed
with good weather conditions and at an airmass of 1.5

Within the enhanced Swift-XRT error circle (Beardmore et al., GCN Circ.
29489) we detect a single extended source with r = 23.17 +/- 0.05 AB mag,
previously reported as the putative host galaxy (Heintz et al., GCN Circ.
29498).

A weak optical source with r = 25.3 +/- 0.2 AB mag lies at the edge of the
XRT error circle, 6 arcsec away from the putative host. We cannot determine
whether it is related to the GRB at present time.

Magnitudes are calibrated against the Pan-STARRS DR1 catalog and not
corrected for Galactic extinction.

We thank the Gemini South staff for rapidly executing these observations.


GRB_name: GRB210213B
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29509
SUBJECT: GRB 210213B: Insight-HXMT/HE detection
DATE:    21/02/15 13:54:32 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

Y. Q. Zhang, C. Cai, J. C. Liu, Q. Luo, S. Xiao, 
W. C. Xue, Q. B. Yi, C. Zhengï¼ŒY. Huang, C. K. Li, 
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 2021-02-13T06:52:27.18 (T0), Insight-HXMT/HE detected 
GRB 210213B (trigger ID: HEB210213286) in a routine search of the data, 
which also triggered CALET (trigger ID:1297234318) and INTEGRAL.

The Insight-HXMT/HE light curve mainly consists of multiple 
pulses with a duration (T90) of 15.33 s measured from T0+1.55 s. 
The 1-ms peak rate, measured from T0+1.66 s, is 5983 cnts/sec. 
The total counts from this burst is 31576 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210213286_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: GRB210212A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29510
SUBJECT: GRB 210212A: 1.3m DFOT Optical upper limit
DATE:    21/02/15 18:26:17 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

Rahul Gupta,  A. Kumar, Dimple,  A. Ghosh, A. Aryan, B. Kumar, S. B.
Pandey, and K. Misra (ARIES) report:

We observed the field of Swift detected GRB 210212A (Troja et al., GCN
29487) with 1.3m Devasthal Fast Optical Telescope (DFOT) located at
Devasthal observatory of Aryabhatta Research Institute of
Observational Sciences (ARIES), India. The observations were started
on 2021-02-13 at 13:54:09 UT i.e. ~ 1.4 days after the BAT trigger. We
have taken multiple frames having an exposure time of 180 s in the R
filter. We did not detect any optical afterglow candidate within the
Swift/XRT enhanced position (Beardmore et al., GCN 29489).


We obtain the following 3-sigma upper limit in the stacked image.


Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Limiting Magnitude

======================================================
2021-02-13 13:54:09   ~1.4          R   180*15      > 22.4



The magnitude is not corrected for the Galactic extinction in the
direction of the burst. Photometric calibration is performed using the
standard stars from the USNO-B1.0 catalogue.

This circular may be cited.


GRB_name: GRB210212B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29511
SUBJECT: IPN triangulation of GRB 210212B (consistent with ZTF21aakruew/AT2021cwd)
DATE:    21/02/15 18:35:45 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. 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 long-duration GRB 210212B has been detected by
Konus-Wind, in the waiting mode, INTEGRAL (SPI-ACS), and
Swift (BAT), so far, at about 9477 s UT (02:37:57).
The burst was likely outside the coded field of view of the BAT.

We have triangulated it to a preliminary, error box
whose coordinates are:
   ---------------------------------
    RA(2000), deg     Dec(2000), deg
   ---------------------------------
   Corners:
       159.26         +24.95
       100.54         +38.07
        96.30         +19.08
       163.83         +2.39
   ---------------------------------
This box may be improved.

The optical transient ZTF21aakruew/AT2021cwd (Yao et al., GCN Circ. 
29508) is inside the box, lending support to the association of the 
transient and the burst.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB210212_T09477/IPN/

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


GRB_name: GRB210212B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29512
SUBJECT: GRB 210212B (TF21aakruew/AT2021cwd): Assy optical observations
DATE:    21/02/16 13:44:36 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Pozanenko (IKI), S. Belkin (IKI), V. Kim (FAI, Pulkovo Observatory), 
Y. Aimuratov (FAI), M. Krugov (FAI), N.Pankov (HSE)  report on behalf of 
GRB IKI FuN

We observed the optical transient of ZTF21aakruew/AT2021cwd (Yao et al., 
GCN 29508) which is probably an afterglow of GRB 210212B (Svinkin et 
al., GCN 29511) with AZT-20 telescope of Assy-Turgen observatory 
starting on 2021-02-15 (UT) 17:33:23. The optical transient is 
marginally detected in a stacked image in r'-filter.

Preliminary photometry of the object  is following
Date       UT start   t-T0    Filter  Exp.   OT    S/N  Err.  UL(3sigma)
                             (mid, days)     (s)

2021-02-15 17:33:23   3.64231  r'     59*60  23.8  2.5  0.5   23.6

The photometry is based on nearby SDSS-DR12 stars
RA DEC r dr
10:24:36.66048 +11:35:29.6088 18.206 0.008
10:24:34.08528 +11:36:05.0220 17.486 0.006
10:24:47.98080 +11:38:11.0832 15.153 0.003

The midtime value (t-T0) given in the table above  was counted from GRB 
trigger of 2021-02-12 (UT) 02:37:57 (Svinkin et al., GCN 29511).

The power-law index  of the light curve (alpha ~ 1.7) is consistent with 
an afterglow after jet break. The light curve can be found in

http://grb.rssi.ru/GRB210212B/GRB210212B_LC.png


GRB_name: GRB210212B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29513
SUBJECT: GRB 210212B: Swift ToO observations
DATE:    21/02/16 15:07:04 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 IPN GRB 210212B. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021423

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 IPN 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: GRB210212B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29514
SUBJECT: Konus-Wind detection of GRB 210212B / ZTF21aakruew
DATE:    21/02/16 16:15:34 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 210212B
(ZTF OT detection: Yao et al., GCN Circ. 29508;
IPN triangulation: Svinkin et al., GCN Circ. 29511)
was detected by Konus-Wind (KW) in the waiting mode.

The burst light curve shows a single emission episode
which starts at about T0=9479 s UT (02:37:59)
and has the total duration of ~48 s.

The K-W light curve of this burst is available at
http://www.ioffe.ru/LEA/GRBs/GRB210212_T09477/

As observed by Konus-Wind, the burst had a fluence of
8.7(-1.1,+1.7)x10^-6 erg/cm2 and a 2.944-s peak flux,
measured from ~T0, of 6.7(-1.6,+4.8)x10^-7 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The K-W 3-channel time-integrated spectrum
(from T0 to T0+48 s) is well described by
a cutoff power-law model with
alpha = -1.24(-0.23,+0.33) and Ep = 208(-46,+84) keV.

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.


GRB_name: GRB210211A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29515
SUBJECT: GRB 210211A: ePESSTO+ NTT optical observations
DATE:    21/02/16 18:08:56 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

L. Harvey, M. Magee (TCD), P. D'Avanzo (INAF-OAB), D. B. Malesani (DTU Space), S. Prentice, M. Deckers (TCD), S. Schulze (OKC), J. Teffs (LJMU), 
S. Gonzalez-Gaitan (CENTRA), J. Anderson (ESO), T. Muller Bravo (Southampton), T.-W. Chen (Stockholm), M. Gromadzki (Warsaw), C. Inserra (Cardiff), 
E. Kankare (Turku), M. Nicholl (Birmingham), O. Yaron (Weizmann), D. Young (QUB), I. Manulis (Weizmann), report:


We observed the field of GRB 210211A (Fermi GBM Team, GCN Circ. 29470; Troja et al., GCN Circ. 29472) under the advanced extended Public ESO 
Spectroscopic Survey for Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org <http://www.pessto.org/> ). The observations were performed 
on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument in imaging mode on 2021-02-16 between 08:01:05 UT and 08:42:23 UT 
(i.e. about 4.99 days from the burst). The observations were carried out with the R filter under a seeing of about 1.9". 

The optical afterglow (D'Avanzo et al., GCN Circ. 29474; Lipunov et al. GCN Circ. 29477; Kuin et al., GCN Circ. 29485) is not detected down to a 3sigma 
limiting magnitude of R ~ 24.3 (Vega; based on preliminary photometry calibrated against the USNO B1 catalogue). 


GRB_name: GRB210210A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29517
SUBJECT: GRB 210210A: Konus-Wind detection and joint Konus-Wind + Swift-BAT spectral analysis
DATE:    21/02/17 14:49:35 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, T. Cline, on behalf of the Konus-Wind team,
and A. Lien (GSFC/UMBC), report:

The long GRB 210210A (Swift-BAT trigger #1031728, T0 = T0(BAT)= 02:00:27.920 UT:
Laha et al., GCN 29444; Lien et al., GCN 29467)
was detected by Konus-Wind (KW) in the waiting mode.

A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band
reveals a ~11 sigma count rate increase over background in the interval
from ~T0(BAT)-1.7 s to ~T0(BAT)+7.1 s.
The KW light curve of this burst is available
at http://www.ioffe.ru/LEA/GRBs/GRB210210A/

To derive the broad-band spectral parameters of this burst, we performed
a joint spectral analysis of the Swift/BAT data (15-150 keV) and the Konus-Wind
3-channel spectral data, which cover the energy range from ~20 keV to ~1.5 MeV.

The time-averaged spectrum, measured from T0(BAT)-1.685 s to T0(BAT)+7.147 s,
is best fit in the 15 keV - 1.5 MeV range by a power law with an exponential cutoff.
This fit gives a photon index alpha -1.68 (-0.23,+0.25), and Ep of 16.6 (-10.7,+7.2) keV
(chi^2 = 47.5/ 58 dof).
A fit to a simple power law gives a photon index of (2.52 Â± 0.07), chi^2 = 58.4/ 59 dof.
The joint fit results are consistent with the Swift-BAT refined analysis (GCN 29467).

In the 15-1500 keV band, the total burst fluence, estimated from the CPL model,
is (1.2 Â± 0.1)x10^-6 erg/cm^2, and the 2.944 s peak energy flux is (2.4 Â± 0.2)x10^-7 erg/cm^2.

Assuming the redshift z=0.715 (de Ugarte Postigo et al., GCN 29450)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to ~1.7x10^51 erg,
the isotropic luminosity L_iso to ~5.9x10^50 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~29 keV.
With these values, GRB 210210A is within 90% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (part II: Tsvetkova et al., ApJ, in press),
see http://www.ioffe.ru/LEA/GRBs/GRB210210A/GRB210210A_rest_frame.pdf

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.


GRB_name: GRB210208A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29518
SUBJECT: GRB 210208A: 1.3m DFOT Optical upper limit
DATE:    21/02/17 19:26:19 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

Rahul Gupta,  A. Kumar, Dimple,  A. Ghosh, A. Aryan, B. Kumar, S. B.
Pandey, and K. Misra (ARIES) report:

We observed the field of INTEGRAL detected GRB 210208A (Mereghetti et
al., GCN 29429) with 1.3m Devasthal Fast Optical Telescope (DFOT)
located at Devasthal observatory of Aryabhatta Research Institute of
Observational Sciences (ARIES), India. The observations were started
on 2021-02-13 at 22:43:42 UT i.e. ~ 5.4 days after the INTEGRAL
trigger. We have taken multiple frames having an exposure time of 180
s in the R filter. We did not detect any optical afterglow candidate
in our single or stacked image within the INTEGRAL uncertainty circle
(Mereghetti et al., GCN 29429). Our non-detection is consistent with
Hu et al., GCN 29439 and Kumar et al., GCN 29451.


We obtain the following 3-sigma upper limit in the stacked image.


Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Limiting Magnitude

======================================================
2021-02-13 22:43:42   ~5.4          R   180*10      > 22.0



The magnitude is not corrected for the Galactic extinction in the
direction of the burst. Photometric calibration is performed using the
standard stars from the USNO-B1.0 catalogue.

This circular may be cited.


GRB_name: GRB210204A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29520
SUBJECT: GRB 210204A (ZTF21aagwbjr/AT2021buv): continued Assy and Mondy optical observations
DATE:    21/02/17 22:55:05 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), V. Kim (FAI, Pulkovo Observatory), 
E. Klunko (ISTP),  N. Pankov (HSE), M. Krugov (FAI) report  on behalf of 
GRB IKI FuN:

We continued observation of the ZTF21aagwbjr/AT2021buv transient (Kool 
et al., GCN 29405) at the redshift of 0.876 (Xu et al., GCN 29432) which 
is  an afterglow (Kennea et al., GCN 29413; Teja  et al., GCN 29414;
Belkin  et al., GCNs 29417, 29438, 29499;   Rossi et al., GCN 29433; 
Gupta et al., GCN 29490) of  GRB 210204A (Fermi GBM team, GCN 29390; Li 
et al., GCN 29392; Hurley et al., GCN 29408; Waratkar et al., GCN 29410; 
  Frederiks et al., GCN 29415). Images in R-filter were obtained at 
AZT-33IK telescope of Sayan observatory (Mondy) on Feb.12, 16 and  in 
r'-filter at AZT-22 telescope of Assy-Turgen observatory on Feb.15, 16.

Preliminary photometry of the optical transient in combined images is 
following

Date       UT start  t-T0     Filter Exp.  OT    Err.  UL(3s) Telescope
                       (mid, days)        (s)

2021-02-12 16:11:09  8.41787  R   20*120 21.66 0.09  22.9  AZT-33IK
2021-02-15 15:40:01 11.40667  r'  70*60  21.86 0.15  23.6  AZT-20
2021-02-16 14:39:53 12.36212  R   31*120 21.8  0.4   21.8  AZT-33IK
2021-02-16 16:57:06 12.44700  r'  32*60  22.18 0.14  23.3  AZT-20

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1014-0149033 15.43
1014-0149115 17.00

and the same stars from SDSS-DR12
SDSS-DR12
RA DEC g dg r dr
117.03151400 +11.42180300 17.036 0.005 15.624 0.005
117.07973400 +11.41971200 17.909 0.006 17.191 0.006

The updated light curve can be found in
http://grb.rssi.ru/GRB210204A/GRB210204A_lc.png


GRB_name: GRB210217A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29521
SUBJECT: GRB 210217A: Swift detection of a burst with an optical counterpart
DATE:    21/02/17 23:36:33 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

K. K. Simpson (PSU), J.D. Gropp (PSU), J. A. Kennea (PSU),
N. J. Klingler (PSU), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU),
D. M. Palmer (LANL), B. Sbarufatti (PSU) and M. H. Siegel (PSU) report
on behalf of the Neil Gehrels Swift Observatory Team:

At 23:25:42 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210217A (trigger=1033264).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 97.610, +68.715 which is 
   RA(J2000) = 06h 30m 26s
   Dec(J2000) = +68d 42' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 5 sec.  The peak count rate
was ~3400 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 23:27:20.1 UT, 97.8 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 97.58675, 68.72497 which
is equivalent to:
   RA(J2000)  = 06h 30m 20.82s
   Dec(J2000) = +68d 43' 29.9"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 47 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 consistent with the Galactic value of 8.69
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 103 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 06:30:19.93 =  97.58305
  DEC(J2000) = +68:43:30.6  =  68.72516
with a 90%-confidence error radius of about 0.63 arc sec. This position is 6.2
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.72 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.103. 

Burst Advocate for this burst is K. K. Simpson (kira.simpson1984 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: GRB210212A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29522
SUBJECT: GRB 210212A: Mondy optical observations
DATE:    21/02/18 00:17:06 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) 
report  on behalf of GRB IKI FuN:

We observed the field of GRB 210212A (Troja et al., GCN 29487) with 
AZT-33IK telescope of Sayan observatory (Mondy) starting on 2021-02-12 
(UT) 14:39:29, i.e. 0.45 days after GRB trigger and reasonable FWHM of 
about 2.7". Within enhanced XRT position (Beardmore et al., GCN 29489) 
we found an object. Preliminary photometry of the object in a combined 
image is following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-02-12 14:39:29   0.44527    R      27*120  22.20 0.28  22.4

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
0972-0060540 15.06
0972-0060545 15.99

The object could be an afterglow of the GRB 210212A which is not 
separated from (possible host) galaxy (Heintz  et al., GCN 29498; 
Dichiara et al., GCN 29507).


GRB_name: GRB210217A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29523
SUBJECT: GRB 210217A: NEXT early optical afterglow observations
DATE:    21/02/18 00:20:00 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210217A (Simpson et al., GCN 29521) using 
the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. 
Observations automatically started at 23:27:06 UT on 2021-02-17, i.e., 
84 s after the BAT trigger. A series of 3x40 s, 4x60 s and 10x90 s 
frames in the Sloan r-filter have been obtained, and observations are 
ongoing.

An uncatalogued decaying optical transient is detected at the Swift/UVOT 
position (Simpson et al., GCN 29521), which is thus concluded to be the 
optical afterglow of burst. The afterglow has r = 18.6 +/- 0.2 mag in 
our first image, calibrated with nearby PS1 stars.


GRB_name: GRB210217A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29525
SUBJECT: GRB 210217A: Enhanced Swift-XRT position
DATE:    21/02/18 03:26:12 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 396 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210217A, 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 = 97.58507, +68.72536 which is equivalent
to:

RA (J2000): 06h 30m 20.42s
Dec (J2000): +68d 43' 31.3"

with an uncertainty of 1.9 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: GRB210205A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29526
SUBJECT: GRB 210205A: observations with the 3.6m DOT, a potential dark burst?
DATE:    21/02/18 09:07:31 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

S. B. Pandey, R. Gupta, A. Kumar, Dimple, A. Ghosh, A. Aryan,  and K. Misra
(ARIES) on behalf of a larger collaboration report:

GRB 210205A was detected by the Swift Burst Alert Telescope (BAT) at
11:11:17 UT on 5th Feb 2021 (GCN 29397). The prompt emission mask-weighted
BAT light curve consists of a multi-peaked structure with a T90 duration of
22.70 +- 4.18 sec in 15-350 keV energy range (GCN 29409). We compare the
reported value of BAT fluence and peak photon flux for this GRB (GCN 29409)
with all the BAT detected samples, we find this burst is positioned nearly
the middle of this distribution. The Swift XRT detected an X-ray afterglow
~ 134.7 sec after the BAT trigger (GCN 29397). The X-ray light curve could
be best described with a simple power-law model with a temporal index of
1.100 (+0.092, -0.101) and the afterglow is fainter (0.016 x 10^-11
erg/cm2/s, at 11-hour post burst) than typical X-ray afterglows. As no
red-shift has been reported for this source, we modeled the time-averaged
XRT spectrum (T0 + 143 to 39716 s) considering red-shift = 2, roughly
average red-shift value for long GRBs. The spectrum could be modeled using
an absorption power-law with following spectral parameters: NH_host= 5.34
(-4.58,+6.18) * 10^{22} cm^{-2} and \beta_x= 1.11 (-0.37,+0.40).
Considering the adiabatic deceleration without energy injection, closure
relations indicate that the X-ray afterglow could be best described with
\nu > \nu_c spectral regime for ISM as well as WIND medium for the electron
energy index p ~ 2.22.

Many optical telescopes searched for the optical afterglow but no
counterpart associated with this burst was detected to deeper limits at
early epochs(GCN  29397, 29398, 29400, 29401, 29402, 29403, and 29406). So,
we performed the search for the optical counterpart of this XRT localized
GRB 210205A (GCN 29399) using the 4Kx4K CCD Imager (Pandey et al. 2017,
arXiv:1711.05422v1) mounted at the axial port of the 3.6m Devasthal Optical
Telescope (DOT) of ARIES Nainital. Multiple frames having exposure times of
300s each were taken in R and I filters.  We do not find any evidence of an
afterglow candidate inside the XRT error circle, consistent with other
non-detections. We constrain the following 3-sigma upper limits.

T-T0 (days) Exp. (s) Filter  OT   UL   Telescope

1.0921       2*300   R       NA   22.8     3.6m DOT
1.1033       2*300    I        NA   22.6     3.6m DOT

The limiting magnitudes quoted are not corrected for the Galactic and Host
extinction in the direction of the burst. Considering no spectral break
between X-ray and optical frequencies, we extrapolated the X-ray spectral
index towards optical frequencies. We found that using reported limiting
values at optical (Galactic extinction corrected) roughly lie below the
extrapolated X-ray power-law slope, suggesting that this burst could be a
potential dark GRB candidate either highly extinguished or as a high
redshift event.

3.6m Devasthal Optical Telescope (DOT) is a recently commissioned facility
in the Northern Himalayan region of India (long:79 41 04E, lat:29 21 40N,
alt:2540m) owned and operated by the Aryabhatta Research Institute of
Observational Sciences (ARIES), Nainital (https://www.aries.res.in).
Authors of this GCN circular thankfully acknowledge consistent support from
the staff members to run and maintain the 3.6m DOT. This circular may be
cited.


GRB_name: GRB210212A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29527
SUBJECT: GRB 210212A: REM early-time optical/NIR upper limits
DATE:    21/02/18 10:12:02 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo, S. Covino, D. Fugazza, A. Melandri (INAF-OAB) on behalf of the REM team, report:

We observed the field of GRB 210212A (Troja et al., GCN Circ. 29487) with the REM 60cm robotic 
telescope located at the ESO premise of La Silla (Chile). The observations were performed starting 
on 2021 February 12 at 04:27:01 UT (i.e. 103 seconds after the burst) at airmass 3.5 and were carried 
in the g, r, i, z, H bands simultaneously. 

From a preliminary analysis of the first set of images, obtained at a mid time of t-t0 = 150 s, we find no 
source at the enhanced XRT position (Beardmore et al., GCN Circ. 29489) down to the following 3sigma 
magnitude upper limits: 

g > 18.2
r > 18.3
i > 17.4
z > 16.1
(AB; calibrated against the Pan-STARRS catalogue); 

H > 15.8 
(Vega; calibrated against the 2MASS catalogue). 


GRB_name: GRB210212B
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29528
SUBJECT: Subject: ZTF21aakruew/AT2021cwd: GROND observations
DATE:    21/02/18 12:18:01 GMT
FROM:    Ana Nicuesa at TLS Tautenburg  <ana@tls-tautenburg.de>

A. Nicuesa Guelbenzu and S. Klose (both TLS Tautenburg) report:

We observed the field of the optical transient ZTF21aakruew/AT2021cwd (Yao
et al., GCN 29508) that was located inside the error box of GRB 210212B
(Svinkin et al., GCN 29511) with GROND (Greiner et al. 2008, PASP 120,
405) mounted at the 2.2m MPG telescope at the ESO La Silla Observatory
(Chile).

Observations were performed at 5:00 UT (midtime) on February 15, 2021,
about 3.1 days after the GRB 210212B trigger. They were executed at an
average seeing of 1.15 arcsec and at an average airmass of 1.3.

The optical transient is detected in the optical but not in the NIR bands.
Based on a 33 min exposure in g'r'i'z' and 30 min in JHK, and we measure
the following preliminary AB magnitudes and upper limits (3 sigma):

g' = 24.16 +/- 0.14,
r' = 23.63 +/- 0.12,
i' = 23.41 +/- 0.21,
z' > 23.3,
J  > 21.7,
H  > 21.1,
K  > 18.1,

calibrated against SDSS and 2MASS field stars. The observed r'-band
magnitude is formally consistent with the observations reported by
Pozanenko et al. (GCN 29512).

After correction for Galactic extinction (E(B-V)=0.04 mag; Ho et al., GCN
29508), the data are in agreement with an SED that follows a power law. We
consider this as evidence that the transient was indeed afterglow light,
confirming its suggested association with GRB 210212B (Svinkin et al., GCN
29511; Svinkin et al., GCN 29514).


We thank R. Lechaume (PUC) for performing the observations.


GRB_name: GRB210218A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29529
SUBJECT: GRB 210218A: Swift detection of a burst
DATE:    21/02/18 13:45:55 GMT
FROM:    Kim Page at U.of Leicester  <klp5@leicester.ac.uk>

B. Sbarufatti (PSU), N. J. Klingler (PSU), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC) and
K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 13:35:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210218A (trigger=1033328).  Swift did not slew 
immediately due to an observing constraint. 
The BAT on-board calculated location is 
RA, Dec 47.291, +35.287 which is 
   RA(J2000) = 03h 09m 10s
   Dec(J2000) = +35d 17' 14"
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 30 sec.  The peak count rate
was ~800 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to a Moon observing constraint, Swift cannot slew to the BAT
position until 11:37 UT on 2021 February 20. There will thus be no XRT
or UVOT data for this trigger before this time. 

Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.edu). 
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: GRB210218A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29530
SUBJECT: GRB 210218A: NEXT optical upper limit
DATE:    21/02/18 14:28:05 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210218A (Sbarufatti et al., GCN 29529) 
using the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, 
China. Observations automatically started at 13:36:52 UT on 2021-02-18, 
i.e., 93 s after the BAT trigger. We obtained 3x40 s, 4x60 s and 12x90 s 
frames in the Sloan r-filter.

No credible optical transient is detected in our stacked image within 
the Swift/BAT error circle, down to a limiting magnitude of r ~ 20.4, 
calibrated with the nearby PanSTARRS field.


GRB_name: GRB210218A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29531
SUBJECT: GRB 210218Aï¼š GWAC-F60A optical upper limit 
DATE:    21/02/18 14:42:03 GMT
FROM:    Liping Xin at NAOC, SVOM  <xlp@nao.cas.cn>

L. P. Xin(NAOC),  J. Wang(GXU), C. Gao(GXU), X. H. Han(NAOC), J. Y. Wei(NAOC), 
G. W. LI(NAOC),  L. H. Li(NAOC), C. Wu(NAOC),  X. G. Wang(GXU), 
E. W. Liang (GXU), R. S. Zhang(NAOC), Y. L. Qiu(NAOC), 
and J. S. Deng(NAOC) report: 

We began to observe GRB 210218A (Sbarufatti al., GCN 29529)
with Xinglong GWAC-F60A telescope, China, at 11:37:45 (UT), 
18th. Feb. 2021, about 146 sec after the burst, under bad seeing condition. 

A series of  R, I images were obtained.
Preliminary analysis shows that no any new optical source
was found in single images within the Swift errorbox (Sbarufatti al., GCN 29529), 
down to the 3 sigma upper limit of 15.0 mag in R band.
The upper limit is calibrated to the USNO B1.0 catalog.

This result is consistent with the previous report (Zhu et al., GCN 29530). 


GRB_name: GRB210218A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29532
SUBJECT: GRB 210218A: MITSuME Akeno optical upper limits
DATE:    21/02/18 15:33:22 GMT
FROM:    Ogawa Futa at Tokyo Institute of Technology  <ogawa@hp.phys.titech.ac.jp>

F. Ogawa, R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210218A (Sbarufatti et al. GCN #29529,
Zhu et al. GCN #29530, Xin et al. GCN #29531)  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 2021-02-18 13:36:05 UT(46
seconds after the Swift BAT trigger). We stacked the images with good
conditions. We did not find any new point sources within the Swift BAT
circle (Sbarufatti et al. GCN #29529) in all three bands.
We obtained the 5-sigma limits of the stacked images as follows.

T0+[sec] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
46 14:03:01 1220 g'>17.3, Rc>17.5, Ic>16.7
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the UCAC4 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: GRB210217A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29533
SUBJECT: GRB 210217A: KAIT Optical Observations
DATE:    21/02/18 17:57:39 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, responded to the Swift GRB 210217A (Simpson et al.,

GCN 29521) starting at ~4.27 hours after the Swift trigger.

A total of 30x60s images were obtained in the clear (roughly R) filters.

We marginally detect the optical afterglow (Simpson et al., GCN 29521;

Zhu et al., GCN 29523) in the coadd image with a mag of 20.8 +/- 0.3,

calibrated to the Pan-STARRS1 catalog.


GRB_name: GRB210217A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29534
SUBJECT: GRB 210217A: Swift-BAT refined analysis
DATE:    21/02/18 18:01:32 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. Sakamoto (AGU), 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),
K. K. Simpson (PSU), 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 210217A (trigger #1033264)
(Simpson et al., GCN Circ. 29521).  The BAT ground-calculated position is
RA, Dec = 97.578, 68.715 deg which is
   RA(J2000)  =  06h 30m 18.6s
   Dec(J2000) = +68d 42' 55.4"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 30%.

The mask-weighted light curve shows a single-peaked FRED-like structure
that starts and peaks at ~T0, and ends at ~T+5 s. T90 (15-350 keV) is
4.22 +- 1.15 sec (estimated error including systematics).

The time-averaged spectrum from T-0.65 to T+4.89 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 2.01 +- 0.16.  The fluence in the 15-150 keV band
is 6.8 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured
from T-0.13 sec in the 15-150 keV band is 5.1 +- 0.5 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/1033264/BA/


GRB_name: GRB210217A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29535
SUBJECT: GRB 210217A: Liverpool Telescope First Hour Observations
DATE:    21/02/18 22:17:33 GMT
FROM:    Manisha Shrestha at Liverpool John Moores U  <m.shrestha@ljmu.ac.uk>

M. Shrestha (Liverpool JMU), R. Smith (LJMU) , A. Melandri (INAF), I.A. Steele (LJMU), S. Kobayashi (LJMU), C. Mundell (Univ. Bath), A. Gomboc (Univ. Nova Gorica), C. Guidorzi (Univ. Ferrara)  report on behalf of a wider collaboration:



We observed the field of Swift GRB 210217A (GCN 29521) with the 2.0m Liverpool Telescope (LT), La Palma on 2021 Feb 17 starting at 23:28:51.056  UT

using the IO:O optical camera in the r, i, and z bands.  Data were calibrated with respect to nearby APASS secondary standard stars for r and i bands

and SDSS secondary standard stars for z band. We confirm the optical counterpart reported by Swift UVOT and NEXT (GCN 29523).



At T=194 seconds after the BAT trigger time, we measure r = 18.51 +/- 0.3 mag which is close to 18.6 +/- 0.2 mag detected by NEXT team (GCN 29523).

The r band light curve made with IO:O observations show a power law decay over the first hour in flux vs time with alpha = 0.48.

At T = 690 seconds after the BAT trigger time, we measure i = 18.77 +/- 0.1 mag and at T = 868 seconds after the trigger we measure z = 18.67 +/-0.1 mag.




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GRB_name: GRB210217A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29536
SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 210217A
DATE:    21/02/18 22:22:40 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

C. Fletcher (USRA) reports on behalf of the Fermi-GBM Team:

Swift-BAT detected GRB 210217A at 23:25:42 UT (GCN 29521). There was no
Fermi-GBM onboard trigger around the event.

An automated, blind search for short gamma-ray bursts below the onboard
triggering threshold in Fermi-GBM identified a high reliability transient 
consistent in both time and location with the Swift BAT event.
Link: https://gcn.gsfc.nasa.gov/notices_gbm_sub/635297147.fermi

The GBM targeted search [1], the most sensitive, coherent search for
GRB-like signals also identified a transient most significantly on the 1.024 s
timescale, with a log likelihood ratio of 72 and a location consistent with
the Swift BAT event. The GBM targeted search event was found with the highest
significance with a "normal" spectrum (Band function with
Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB.

[1] Goldstein et al. 2019 arXiv:1903.12597


GRB_name: GRB210218A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29537
SUBJECT: GRB 210218A: Swift-BAT refined analysis
DATE:    21/02/19 02:01:49 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@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), B. Sbarufatti (PSU),
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 210218A (trigger #1033328)
(Sbarufatti et al., GCN Circ. 29529).  The BAT ground-calculated position is
RA, Dec = 47.318, 35.322 deg which is
   RA(J2000)  =  03h 09m 16.3s
   Dec(J2000) = +35d 19' 18.9"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 57%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T-15 s and peaks at ~T0. The burst emission lasted
until the burst went out of the BAT FOV at T+287 s.
Using the available data, the lower limit of T90 is ~ 240 s.

The time-averaged spectrum from T-14.27 to T+266.26 sec is best fit by
a power law with an exponential cutoff.  This fit gives a photon
index 0.77 +- 0.49, and Epeak of 91.3 +- 48.2 keV (chi squared 50.53
for 56 d.o.f.).  For this model the total fluence in the 15-150 keV
band is 4.3 +- 0.3 x 10^-6 erg/cm2 and the 1-sec peak flux measured
from T+0.09 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec.
A fit to a simple power law gives a photon index of 1.46 +- 0.11
(chi squared 57.43 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/1033328/BA/


GRB_name: GRB210217A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29538
SUBJECT: GRB 210217A: Swift-XRT refined Analysis
DATE:    21/02/19 02:58:08 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 6.8 ks of XRT data for GRB 210217A (Simpson et al. GCN
Circ. 29521), from 109 s to 80.4 ks after the  BAT trigger. The data
are entirely in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Evans et al. (GCN Circ. 29525).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.79 (+/-0.05).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.97 (+0.23, -0.22). The
best-fitting absorption column is  2.5 (+0.9, -0.8) x 10^21 cm^-2, in
excess of the Galactic value of 8.7 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 (5.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      2.5 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 8.7 x 10^20 cm^-2
Excess significance: 3.3 sigma
Photon index:      1.97 (+0.23, -0.22)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01033264.

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


GRB_name: GRB210217A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29539
SUBJECT: GRB 210217A: 1.3m DFOT optical detection
DATE:    21/02/19 19:32:22 GMT
FROM:    Amit Kumar at ARIES, India  <amitkundu515@gmail.com>

Amit Kumar (ARIES), Rahul Gupta (ARIES), Ankur Ghosh (ARIES), Dimple
(ARIES), Tushar Tripathi (ARIES), Shubham Kishore (ARIES), Amar Aryan
(ARIES), Shashi B. Pandey (ARIES), Brajesh Kumar (ARIES), and Kuntal Misra
(ARIES) report:

We observed the optical afterglow of the Swift detected GRB 210217A
(Simpson et al. GCN 29521; Evans et al., GCN 29525) with the 1.3m Devsthal
Fast Optical Telescope (DFOT) at Aryabhatta Research Institute of
Observational Sciences (ARIES), Nainital (India), on 2021-02-18 from UT
17:31:22 to 19:09:31 (corresponding to 18.094 to 19.730 hours from the GRB
trigger time). We observed a series of 30x120s exposures in the Bessel R
filter and a series of 20x120s exposures in the Bessel I filter. We clearly
detected the optical afterglow of GRB 210217A in the stacked frames within
the Swift XRT error circle (Simpson et al. GCN 29521) as also reported by
Zhu et al., GCN 29523; Zheng & Filippenko GCN 29533; Shrestha et al. GCN
29535.

The estimated preliminary magnitudes are as follows:

T_start-T0 (hours) Start Date (UTC) Filter Magnitude (mag)
-----------------------------------------------------------
-----------------------------------------------------------
18.09 2021-02-18T17:31:22 R 21.80 +- 0.08
19.73 2021-02-18T19:09:31 I 21.56 +- 0.12

The magnitudes are not corrected for the Galactic extinction in the
direction of the burst. Photometric calibration is performed using the
standard stars from the USNO-B1.0 catalog.

This circular may be cited.


GRB_name: GRB210212A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29540
SUBJECT: GRB 210212A: Lowell Discovery Telescope observations
DATE:    21/02/19 23:47:59 GMT
FROM:    Simone Dichiara at UMCP/NASA/GSFC  <dichiara@umd.edu>

S.Dichiara (UMD, NASA-GSFC) and E. Troja (UMD, NASA-GSFC) report:

We observed the field of GRB 210212A (Troja et al., GCN Circ. 29487)
using the Large Monolithic Imager (LMI) on the 4.3m Lowell Discovery
Telescope (LDT) at Happy Jack, AZ. Observations started on February 19,
at 03:55:50 UT (about 7 days after the Swift trigger) with SDSS g, r, i
and z filters.

The extended source previously reported by Heintz et al. (GCN Circ.
29498) and Dichiara et al. (GCN Circ. 29507) is detected in all bands.
We measure a magnitude of r~23.3 +/- 0.2 AB calibrated against the
Pan-STARRS DR1 catalog and not corrected for Galactic extinction. A
comparison to earlier epochs shows no significant rebrightening.

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


GRB_name: GRB210204A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29541
SUBJECT: uGMRT radio detection of GRB 210204A
DATE:    21/02/22 11:21:18 GMT
FROM:    Poonam Chandra at TIFR  <poonam@ncra.tifr.res.in>

Poonam Chandra (NCRA-TIFR), Varun Bhalerao (IIT-B), Kuntal Misra (ARIES) 
and G. C. Anupama (IIA) report on behalf of a larger collaboration:

We carried out radio observations of GRB 210204A (GCN#29390)  with the 
upgraded Giant Metrewave Radio Telescope (uGMRT) in uGMRT band 5 
(1000-1450 MHz). The observations were taken on 2021 Feb 20 and the 
preliminary flux at at a position RA, Dec(J2000) 07:48:19.345, 11:24:33.91 
is ~140 uJy. The uncertainty in the measurements is ~20 uJy.

Further observations are planned. We thank GMRT staff for making these
observations possible.


GRB_name: GRB210218A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29542
SUBJECT: GRB 210218A: Swift-XRT observations
DATE:    21/02/22 15:30:25 GMT
FROM:    Boris Sbarufatti at PSU  <bxs60@psu.edu>

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

We have analysed 2.7 ks of Photon Counting (PC) mode XRT data for the
Swift-BAT-detected burst GRB 210218A (Stamatikos et al. GCN Circ.
29537), collected between T0+170 ks  and T0+210 ks s. 

One uncatalogued X-ray source has been detected consistent with being
within 296 arcsec of the Swift-BAT position, it is below the RASS limit
and shows no definitive signs of fading. Therefore, at the present time
we cannot confirm this as the afterglow. Details of this source are
given below:

Source 3:
  RA (J2000):  47.3236  =  03:09:17.67
  Dec (J2000): +35.3240  =  +35:19:26.5
  Error: 4.8 arcsec (radius, 90% conf.)
  Count-rate: (5.6 [+2.0, -1.6])e-3 ct s^-1   
  Distance: 164 arcsec from Swift-BAT position.
  Flux: (1.03 [+0.36, -0.29])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)


Two 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/01033328.

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


GRB_name: GRB210222A
Detection_method: MAXI Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29543
SUBJECT: GRB 210222A: MAXI/GSC detection
DATE:    21/02/22 20:18:01 GMT
FROM:    Motoko Serino at RIKEN/MAXI  <motoko@crab.riken.jp>

M. Nakajima (Nihon U.), M. Serino (AGU), Y. Kawakubo (LSU),
H. Negoro, M. Aoki, K. Kobayashi, R. Takagi, K. Asakura, K. Seino (Nihon U.),
T. Mihara, T. Tamagawa, M. Matsuoka (RIKEN),
T. Sakamoto, S. Sugita, H. Nishida, K. Komachi, A. Yoshida (AGU),
Y. Tsuboi, W. Iwakiri, R. Sasaki, H. Kawai, Y. Okamoto, S. Kitakoga (Chuo U.),
M. Shidatsu (Ehime U.),
N. Kawai, R. Adachi, 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, K. Kurogi, K. Miike (Miyazaki U.),
T. Kawamuro (UDP/NAOJ),
K. Yamaoka (Nagoya U.),
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 2021-02-22T15:59:19 UT.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (353.129 deg, -29.464 deg) = (23 32 30, -29 27 50) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.11 deg and 0.04 deg, respectively.
The roll angle of long axis from the north direction is 90.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 389 +- 38 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at 14:26 UT
with an upper limit of 20 mCrab.


GRB_name: GRB210222B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29545
SUBJECT: GRB 210222B: Swift detection of a burst with an optical counterpart
DATE:    21/02/22 23:02:05 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU),
N. P. M. Kuin (UCL-MSSL), F. E. Marshall (NASA/GSFC),
M. J. Moss (GWU), D. M. Palmer (LANL) and B. Sbarufatti (PSU) report
on behalf of the Neil Gehrels Swift Observatory Team:

At 22:37:26 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210222B (trigger=1034325).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 154.621, -14.898 which is 
   RA(J2000) = 10h 18m 29s
   Dec(J2000) = -14d 53' 52"
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 20 sec.  The peak count rate
was ~1250 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 22:39:02.1 UT, 95.9 seconds after
the BAT trigger. Using promptly downlinked data we find an X-ray source
with an enhanced position: RA, Dec 154.6062, -14.9316 which is
equivalent to:
   RA(J2000)  = 10h 18m 25.50s
   Dec(J2000) = -14d 55' 53.7"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 131 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 (8.87 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3
(+1.87/-1.66) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of nominal 150.000 seconds with the White
filter starting 100 seconds after the BAT trigger. There is a candidate
afterglow in the list of sources generated on-board at
  RA(J2000)  = 10:18:25.45 = 154.60606
  DEC(J2000) = -14:55:55.7  = -14.93215
with a 90%-confidence error radius of about 1.10 arc sec. This position is 2.0
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.65. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.101. 

This source lies within the current (Sector 35) field-of-view of TESS camera 1. 

We note that this source is 32 arcseconds from the known ROSAT All-Sky 
X-ray Survey source 1RXS J101827.6-145604.  This is outside of the nominal 
joint error radius and so we believe that the ROSAT source is a 
coincidental alignment unrelated to the new GRB and its optical counterpart. 


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29546
SUBJECT: GRB210222B: BOOTES-1 optical afterglow detection
DATE:    21/02/22 23:16:50 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

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, A. Reina (Univ. de Malaga) and F. Rendon (IAA-CSIC and INTA-CEDEA) on behalf of a larger collaboration, report:

Following the Swift trigger of GRB 210222B (Gropp et al. GCNC 29545), the 0.3m BOOTES-1B robotic telescope in Mazagon (Huelva), southern Spain, automatically responded to this burst. Images were taken starting at 22:40:53 UT (~3.5 min after trigger). In the first 10s image, the afterglow reported by UVOT (Gropp et al. GCNC 29545) is detected with magnitude of 15.6 +/- 0.15 (clear filter). Further observations are ongoing.

We thank the staff at INTA-CEDEA for their excellent support.


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29547
SUBJECT: GRB210222B: LCO Optical Afterglow Detection
DATE:    21/02/22 23:42:26 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 210222B (Gropp et al., GCN 29545) with the LCO 1-m Sinistro instrument at the Sutherland, South Africa site, on February 22, from 22:53 to 23:06 UT (corresponding to 0.27 to 0.43 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 3x120s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent with the initial UVOT detection (Gropp at al., GCN 29444); this source is not present in either USNO or 2MASS catalogs.  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 16.95 +/- 0.01

I = 16.32 +/- 0.01

These magnitudes are not corrected for galactic extinction.

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


GRB_name: GRB210222B
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29548
SUBJECT: GRB 210222B: GOTO confirmation of afterglow detection
DATE:    21/02/23 00:25:43 GMT
FROM:    Travis Mong at Monash University  <yik.mong@monash.edu>

Y-L Mong (1); K. Wiersema (2); K. Tse (1); K. Ackley (1); D. K. Galloway
(1); M. Dyer (3); J. Lyman (2); K. Ulaczyk (2); D. Steeghs (2); V. Dhillon
(3); P. O'Brien (4); G. Ramsay (5); S. Poshyachinda (6); R. Kotak (7); L.
Nuttall (8); D. Pollacco (2); R. Breton (9)

((1) Monash University, (2) Warwick University, (3) University of
Sheffield, (4) University of Leicester, (5) Armagh Observatory &
Planetarium, (6) National Astronomical Research Institute of Thailand, (7)
University of Turku, (8) University of Portsmouth, (9) University of
Manchester) report on behalf of the GOTO collaboration:

We carried out observations with the Gravitational-wave Optical

Transient Observer (GOTO) on La Palma in response to GRB 210222B

(Gropp et al; GCN 29545).

We made a series of 4x90 s exposures using our wide L-band filter

(400-700 nm) covering the Swift XRT error box, beginning around 54 s after
the trigger, with midtime of the first observation 22:42:05.21 UT on 22
February 2021.

We detect an uncatalogued source located at (J2000):

RA 10:18:25.42

Dec +53:24:55.89

confirming the OT reported by MASTER (Lupinov et al.; GCN 29544),

BOOTES-1 (Malesani et al.; GCN 29546) and LCO (Strausbaugh et al.; GCN
29547). We find an equivalent magnitude of g = (16.58 +/- 0.03) mag based
on calibration against PanSTARRS DR1 photometry in ATLAS_REFCAT2 (Tonry et
al. 2018).

Observations are continuing.

GOTO is operated at the La Palma observing facilities of the University

of Warwick on behalf of a consortium including the University of

Warwick, Monash University, Armagh Observatory, the University of

Leicester, the University of Sheffield, the National Astronomical

Research Institute of Thailand (NARIT), Turku University, Portsmouth
University,

Manchester University and the Instituto de Astrofisica

de Canarias (IAC) (https://goto-observatory.org)


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29549
SUBJECT: GRB 210222B: Liverpool Telescope optical detection
DATE:    21/02/23 00:32:17 GMT
FROM:    Daniel Perley at Liverpool JMU  <d.a.perley@ljmu.ac.uk>

D. A. Perley (LJMU) reports:

A short ugriz imaging sequence of the optical afterglow of GRB 210222A 
(Gropp et al. 29545) was obtained using IO:O on the robotic Liverpool 
Telescope between 23:39 and 23:50 UT on 2021-02-22.  Photometry relative 
to PS1 standards in the field gives the following magnitudes:

t-t0 (d)      magnitude
0.04333 :  g = 18.67 +/- 0.04
0.04440 :  r = 18.21 +/- 0.03
0.04544 :  i = 18.01 +/- 0.03
0.04971 :  z = 17.83 +/- 0.06

The g-band photometry lies below an extrapolation of the other bands and 
the source is not detected in u-band, which may suggest a moderately 
high redshift.











DisclaimerNone


GRB_name: GRB210222B
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29550
SUBJECT: GRB 210222B: GOTO confirmation of afterglow detection (correction to GCN29548)
DATE:    21/02/23 01:05:06 GMT
FROM:    Travis Mong at Monash University  <yik.mong@monash.edu>

Y-L Mong (1); K. Wiersema (2); K. Tse (1); K. Ackley (1); D. K. Galloway
(1); M. Dyer (3); J. Lyman (2); K. Ulaczyk (2); D. Steeghs (2); V. Dhillon
(3); P. O'Brien (4); G. Ramsay (5); S. Poshyachinda (6); R. Kotak (7); L.
Nuttall (8); D. Pollacco (2); R. Breton (9)

((1) Monash University, (2) Warwick University, (3) University of
Sheffield, (4) University of Leicester, (5) Armagh Observatory &
Planetarium, (6) National Astronomical Research Institute of Thailand, (7)
University of Turku, (8) University of Portsmouth, (9) University of
Manchester) report on behalf of the GOTO collaboration:

The declination (Dec) of the afterglow candidate reported in GCN29548 is
incorrect. The correct position of the detection is

RA 10:18:25.42
Dec -14:55:54:63

We apologize for any confusion.

GOTO is operated at the La Palma observing facilities of the University of
Warwick on behalf of a consortium including the University of Warwick,
Monash University, Armagh Observatory, the University of Leicester, the
University of Sheffield, the National Astronomical Research Institute of
Thailand (NARIT), Turku University, Portsmouth University, Manchester
University and the Instituto de Astrofisica de Canarias (IAC) (
https://goto-observatory.org)


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29551
SUBJECT: GRB 210222B: NEXT early optical afterglow observations
DATE:    21/02/23 05:05:58 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210222B (Gropp et al., GCN 29545) using the 
NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. 
Observations automatically started at 22:39:01 UT on 2021-02-22, i.e., 
95 s after the BAT trigger. We obtained a series of 40 s and 60 s frames 
during the local morning twilight in the Sloan r-filter.

The previously reported optical afterglow (Gropp et al., GCN 29545; Hu 
et al., GCN 29546; Strausbaugh et al., GCN 29547; Mong et al., GCN 
29548, 29550; Perley et al., GCN 29549) is detected in the stacked 
images of the first three exposures, with r = 14.5 +/- 0.3 mag, 
calibrated with nearby PS1 stars.


GRB_name: GRB210222B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29552
SUBJECT: GRB 210222B: Redshift from FORS2/VLT
DATE:    21/02/23 08:49:55 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte@iaa.es>

J. F. Agui Fernandez (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), L. Izzo (DARK/NBI), D. Xu (NAOC), D.A. Kann (HETH/IAA-CSIC), D.B. Malesani (DTU Space), J.P.U. Fynbo (DAWN/NBI), K. Wiersema (Warwick U.) report:

We observed the afterglow of GRB 210222B (Gropp et al. GCN 29545; Hu et al. GCN 29546; Strausbaugh et al. GCN 29547; Mong et al. GCN 29548 and GCN 29550; Perley GCN 29549; Zhu et al. GCN 29551) with FORS2, mounted at the Unit Telescope 1 of the Very Large Telescope, at Paranal Observatory, Chile. The observation started at 3:00 UT (4.376 hr after the burst) and consisted of 2x700 s exposures using grism 300V and 2x700 s exposures using grism 300I, which together cover the full range between 3300 and 10100 AA.

In the acquisition image, the afterglow is well detected at V = 19.6 +/- 0.1 mag (Vega).

The spectrum shows continuum over the full range with strong absorption features that we identify as due to Lyman alpha, SII, SiII, SiII*, OI, CII, SiIV, CIV, FeII, AlII and MgII at a common redshift of 2.198, which we identify as the redshift of the GRB. This is consistent with the moderately high redshift already reported by Perley (GCN 29549) based on the photometric decline in the u-band.

We acknowledge excellent support from the ESO staff, in particular Jose Velasquez, Chiara Mazzucchelli, and Jonathan Smoker.


GRB_name: GRB210222A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29553
SUBJECT: GRB 210222A: CALET Gamma-Ray Burst Monitor detection
DATE:    21/02/23 10:08:53 GMT
FROM:    Valentin Pal'shin at AGU  <val@phys.aoyama.ac.jp>

P. S. Marrocchesi (U of Siena),
A. Yoshida, T. Sakamoto, 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),
and the CALET collaboration:

At 15:57:23.469 UTC on 22 February 2021, the CALET Gamma-ray Burst
Monitor (CGBM) triggered on long GRB 210222A
(http://cgbm.calet.jp/cgbm_trigger/flight/1298044600/),
which was also detected by the MAXI/GSC at T0(CGBM)+116 s
(Nakajima et al., GCN Circ. 29543).
The burst signal was seen by all CGBM detectors.

The burst light curve shows a FRED-like pulse which starts at T+0.6 sec,
peaks at T+7.5 sec, and ends at T+87.3 sec. The T90 and T50 durations
measured by the SGM data are 71.4 +- 11.5 sec and 33.5 +- 4.4 sec
(40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1298044600/

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


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29554
SUBJECT: GRB 210222B: MASTER OT observation 
DATE:    21/02/23 11:10:04 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin, 
V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
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)
automatically started (Lipunov et al. GCN 29544)
Swift  GRB 200222B (J.Gropp et al. GCN 29545,Ttrigger=22:37:26 UT)
optical observations at MASTER-Kislovodsk at 2021-02-22 22:38:07UT (41s 
after trigger time in clouds),
at MASTER-SAAO at 2021-02-22 22:42:03UT (GCN 29544).

MASTER auto-detection system found MASTER OT J101825.41-145554.9,
also detected by Swift (GCN 29545), and observed by BOOTES-1 (GCN 29546), 
LCO (29547), GOTO(29548), Liverpool Telescope (GCN 29549), NEXT (29551),VLT (GCN 29551)
This OT was also observed by MASTER-IAC.

The reduction of MASTER wide field and very wide field cameras images will be 
continued.
This message may be cited.


GRB_name: GRB210217A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29555
SUBJECT: GRB 210217A: Swift/UVOT Detection
DATE:    21/02/23 14:27:28 GMT
FROM:    Kira Simpson at PSU  <kira.simpson1984@gmail.com>

GRB 210217A: Swift/UVOT Detection

K. K. Simpson (PSU) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210217A
103 s after the BAT trigger (Simpson et al., GCN Circ. 29521).
A source consistent with the XRT position
*** POSITION REFERENCE is GCN_Notice ***
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  06:30:19.90 =  97.58291 (deg.)
    Dec (J2000) = +68:43:30.6  =  68.72517 (deg.)
with an estimated uncertainty of 0.46 arc sec. (radius, 90% confidence).

Preliminary detections 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              103          253          147         18.80 +/- 0.06
u                  315          508          190         18.64 +/- 0.11

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.102 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210218A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29556
SUBJECT: GRB 210218A: Swift/UVOT observations
DATE:    21/02/23 14:49:18 GMT
FROM:    Alexander Belles at PSU/Swift  <aub1461@psu.edu>

A. Belles (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210218A
approximately 170 ks after the BAT trigger (B. Sbarufatti et al., GCN 29529)
due to a Moon constraint. No optical afterglow consistent with the XRT
candidate position is detected (Osborne et al., GCN 29542).

Preliminary 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first exposure
is:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
wh           170031       188263         1665            >21.65

The magnitude in the table is not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.19 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210222B
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29557
SUBJECT: GRB 210222B: FRAM-ORM afterglow detection
DATE:    21/02/23 15:53:50 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

Martin Jelinek and Jan Strobl (ASU CAS Ondrejov, CZ),
Sergey Karpov, Martin Masek, Petr Janecek, Jakub Jurysek,
Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza
(Institute of Physics, Prague, CZ)

report:

The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted robotically
to the alert of GRB210222B (Gropp et al. GCNC 29545, Marrocchesi et al.
GCNC 29553), obtaining a series of 20 s unfiltered images starting at
22:38:21.1 UT, i.e. 55.1s post trigger.

We clearly detect the source reported by other telescopes (Hu et al. GCNC
29546, Strausbaugh et al. GCNC 29547, Mong et al. GCNC 29548, Perley GCNC
29549, Agui Fernandez et al. GCNC 29552, and Lipunov et al. GCNC 29554). As
seen by FRAM, the brightness of the object reached a maximum of about
R(Vega) ~ 15.5, similarly to the value of BOOTES, and then slowly changed
to a decay with an index alpha = ~1.1.

Would the decay stay at this rate, the afterglow may have a brightness of
R~22.0 24h post trigger.


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29558
SUBJECT: GRB 210222B: KAIT Optical Upper Limit
DATE:    21/02/23 16:48:01 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, responded to Swift GRB 210222B (Gropp et al.,

GCN 29545) starting at ~0.44 days after the burst. A total of

30x60s images were obtained in the clear (roughly R) filters.

We do not detect the optical afterglow (Gropp et al., GCN 29545;

Hu et al., GCNC 29546; Strausbaugh et al., GCNC 29547; Mong et al.,

GCNC 29548; Perley, GCNC 29549; Agui Fernandez et al., GCNC 29552;

Lipunov et al., GCNC 29554; Jelinek et al., GCN 29557) in the

co-add images, down to a limiting magnitude of ~20.0 mag calibrated

to the USNOB1.0 catalog.


GRB_name: GRB210222B
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29559
SUBJECT: GRB 210222B: Swift/UVOT Detection
DATE:    21/02/23 18:57:39 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (PSU) and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210222B
101 s after the BAT trigger (Gropp et al., GCN Circ. 29545).
A source consistent with the XRT position (Gropp et al. GCN Circ. 29545)
is detected in the initial UVOT exposures. This source is also consistent
with previously reported optical detections (Hu et al., GCN Circ. 29546; 
Strausbaugh, GCN Circ. 29547; Mong et al., GCN Circ. 29548; Parley, GCN Circ.
29549; Zhu et al., GCN Circ. 29551, Lipunov et al., GCN Circ. 29554). We note
that the lack of detection in the NUV passbands would be consistent with the
redshift of 2.198 reported by Agui Fernandez et al. (GCN Circ. 29552).

The preliminary UVOT position is:
   RA  (J2000) =  10:18:25.43 = 154.60595 (deg.)
   Dec (J2000) = -14:55:55.1  = -14.93198 (deg.)
with an estimated uncertainty of 0.42 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              101          250          147         16.89 +/- 0.03
v                  588          608           19         16.80 +/- 0.17
b                  515          534           20         17.24 +/- 0.12
u                  259          508          246         16.82 +/- 0.04
w1                 639         1793          124        >18.8
m2                 614         1606           78        >20.1
w2                 564         1732          136        >19.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.102 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210222B
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29560
SUBJECT: GRB 210222B: Swift-XRT refined Analysis
DATE:    21/02/23 19:23:17 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 6.2 ks of XRT data for the Swift-BAT-detected burst
GRB 210222B (Gropp et al. GCN Circ. 29545), from 111 s to 63.2 ks after
the  Swift-BAT trigger. The data are entirely in Photon Counting (PC)
mode. Using 2754 s of PC mode data and 4 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 = 154.60574, -14.93170
which is equivalent to:

RA (J2000): 10h 18m 25.38s
Dec(J2000): -14d 55' 54.1"

with an uncertainty of 1.4 arcsec (radius, 90% confidence). This
position is 2.2 arcmin from the Swift-BAT position. 

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.19 (+/-0.16), followed by a break at T+827 s to an
alpha of 1.30 (+0.12, -0.08).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.98 (+0.15, -0.14). The
best-fitting absorption column is  1.4 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 8.9 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 (4.4 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.4 (+0.5, -0.4) x 10^21 cm^-2
Galactic foreground: 8.9 x 10^20 cm^-2
Excess significance: 1.9 sigma
Photon index:      1.98 (+0.15, -0.14)

If the light curve continues to decay with a power-law decay index of
1.30, the count rate at T+24 hours will be 3.1 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 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/01034325.

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


GRB_name: GRB210222B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29561
SUBJECT: GRB 210222B: Swift-BAT refined analysis
DATE:    21/02/23 22:42:22 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

T. N. Ukwatta (LANL), 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), B. Sbarufatti (PSU)
M. Stamatikos (OSU), (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 210222B (trigger #1034325)
(Gropp et al., GCN Circ. 29545).  The BAT ground-calculated position is
RA, Dec = 154.631, -14.946 deg which is
   RA(J2000)  =  10h 18m 31.4s
   Dec(J2000) = -14d 56' 45.7"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 38%.

The BAT light curve showed a two peaked structure with a duration of about ~20 sec.
T90 (15-350 keV) is 12.82 +- 1.28 sec (estimated error including systematics).

The time-averaged spectrum from T-11.37 to T+2.72 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.37 +- 0.33.  The fluence in the 15-150 keV band is 3.4 +- 0.7 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.87 sec in the 15-150 keV band
is 1.4 +- 0.3 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/1034325/BA/


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29562
SUBJECT: GRB 210222B: VIRT optical detection
DATE:    21/02/24 04:10:56 GMT
FROM:    Priyadarshini Gokuldass at U. of the Virgin Islands  <priyadass.94@gmail.com>

P. Gokuldass (UVI), N. Orange (OrangeWave Innovative Science, LLC), R.
Strausbaugh (UVI), A. Cucchiara (UVI/College of Marin),
D. Morris (UVI) report:

We observed the field of GRB210222B (Gropp et al, GCN 29545) with the
0.5m Virgin Island Robotic Telescope (VIRT)
at the University of the Virgin Islands' Etelman Observatory on
02-23-2021 starting at 02:14:31 UT (T+3.6hrs).
We performed a series of exposures in R filter with a total exposure
of 4600 s. The weather conditions were clear
during the hours of observation with an average air masses as shown in
the table below.

We detect the optical transient reported by others (Gropp et al., GCN
29545, Hu et al., GCN 29546,Strausbaugh et al.,
GCN 29547, Mong et al., GCN 29548, Perley, GCN 29549, Aqui Fernandez
et al., GCN 29552, Lipunov et al., GCN 29554,
Jelinik et al., GCN 29557) at > 3-sigma confidence with magnitudes as
reported below:

T_mid       ||Exposure     ||Filter      ||Limit         ||Airmass
T+4.5 hrs   ||2000s        ||R           ||18.5 +/- 0.1  ||1.7
T+8.5 hrs   ||2600s    ||R           ||20.0 +/- 0.2  ||1.5

The magnitude is estimated from comparison to nearby USNO B1 stars and
is not corrected for Galactic extinction.
Further analysis is in progress. The VIRT is still in the commissioning phase.

This work is supported by NASA-MUREP-MIRO grant NNX15AP95A, NSF EiR
AST Award 1901296, and NSF HBCU-UP AST Award 1831682.
This message can be cited.


GRB_name: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29563
SUBJECT: GRB 210222B: Zeiss-1000 of Koshka observatory, optical observations
DATE:    21/02/24 11:08:10 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI),  A. Novichonok (Petrozavodsk State 
University, KIAM),  A. Zhornichenko (KIAM),  N. Pankov (HSE)  report  on 
behalf of IKI GRB FuN:

We observed the field of  GRB 210222B (Gropp et al., GCN 29545) with 
Zeiss-1000 telescope of Koshka observatory starting on Feb. 22 (UT) 
22:46:13, i.e. about 12.8 minutes after GRB trigger. We clearly detect 
optical afterglow  (Gropp et al., GCN 29545; Hu et al., GCN 29546; 
Strausbaugh et al., GCN 29547; Mong et al., GCNs 29548, 29550; Perley et 
al., GCN 29549; Zhu et al., GCN  29551;  Lipunov  et al., GCN 29554; 
Jelinek  et al., GCN 29557; Zheng et al., GCN 29558; Siegel et al., GCN 
29559; Gokuldass et al., GCN 29562). Observations were performed under 
non-optimal weather conditions.

Preliminary photometry of the afterglow is following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2020-12-03 20:50:46   0.58216    R      120*25   n/d  n/d   20.5

Date,       UT start  Exptime,s t-T0,d   Filter OT    Err  UL(3sigma)
2021-02-22 22:46:13     240   0,00748842 R      16.27 0.09 18.3
2021-02-22 22:50:18     240   0,01032407 R      16.49 0.11 18.2
2021-02-22 22:55:50     240   0,01416666 R      16.71 0.11 18.2
2021-02-22 22:59:54    5*240  0,02254629 R      17.18 0.18 18.7
2021-02-22 23:20:18    7*240  0,03949074 R      17.60 0.15 18.9


The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
0750-0233028 14.52
0750-0233056 15.22
0750-0233031 15.24

The light curve can be found in
http://grb.rssi.ru/GRB210222B/GRB210222B_LC.png
Based only on our photometry we estimated power law index of the 
afterglow light curve of -0.74.

We are grateful to the â€œTerskol Observatoryâ€ Center of the Institute of 
Astronomy of the Russian Academy of Sciences (INASAN) for  the 
observations with the Zeiss-1000 telescope on Mount Koshka at the Simeiz 
Observatory.


GRB_name: GRB210222A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29564
SUBJECT: Konus-Wind detection of GRB 210222A
DATE:    21/02/24 15:02:52 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 long GRB 210222A (MAXI/GSC detection: Nakajima et al., GCN 29543;
CALET Gamma-Ray Burst Monitor detection: Marrocchesi et al., GCN 29553)
was detected by Konus-Wind (KW) in the waiting mode starting from
~T0 = 57443.990 (15:57:23.990) UT (or ~2 minutes before the MAXI trigger).

A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band
reveals a ~30 sigma count rate increase over background in the interval
from ~T0 to ~T0+177 s.
The KW light curve of this burst is available
at http://www.ioffe.ru/LEA/GRBs/GRB210222A/

Modeling the KW 3-channel time-integrated spectrum
(measured from T0+0.115 s to T0+176.755 s)
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.33(-0.11,+0.15) and Ep = 317(-72,+108) keV.

A CPL fit to the spectrum near the peak count rate,
measured from T0+0.115 s to T0+14.835 s, gives
alpha -0.48(-0.14,+0.15), and Ep of 375(-40,+40) keV.

In the 10 keV -10 MeV band, the total burst fluence is (4.2 Â± 0.6)x10^-5 erg/cm^2,
and the 2.944 s peak energy flux is (9.3 Â± 0.8)x10^-7 erg/cm^2.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.


GRB_name: GRB210222B
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29565
SUBJECT: GRB 210222B: MITSuME Akeno optical upper limits
DATE:    21/02/25 08:30:41 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210222B (Lipunov et al. GCN #29544, Gropp
et al. GCN #29545, Hu et al. GCN #29546, Strausbaugh et al. GCN
#29547, Mong et al. GCN #29548, Perley et al. GCN #29549, Mong et al.
GCN #29550, Zhu et al. GCN #29551, Fernandez et al. GCN #29552,
Lipunov et al. GCN #29554, Jelinek et al. GCN #29557, Zheng et al. GCN
#29558, Siegel et al. GCN #29559, Page et al. GCN #29560, Ukwatta et
al. GCN #29561, Gokuldass et al. GCN #29562, Belkin et al. GCN #29563)
 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
2021-02-23 11:00:13 UT(12.4hours after the Swift BAT trigger). We
stacked the images with good conditions. We did not detect the optical
afterglow reported previously (Gropp et al. GCN #29545, Hu et al. GCN
#29546, Strausbaugh et al. GCN #29547, Mong et al. GCN #29548, Perley
et al. GCN #29549, Mong et al. GCN #29550, Zhu et al. GCN #29551,
Fernandez et al. GCN #29552, Lipunov et al. GCN #29554, Jelinek et al.
GCN #29557, Siegel et al. GCN #29559, Gokuldass et al. GCN #29562,
Belkin et al. GCN #29563) 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
------------------------------------------------------------------------------------------------
12.4 15:18:25 14100 g'>19.6, Rc>19.9, Ic>19.2
------------------------------------------------------------------------------------------------
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: GRB210222B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29567
SUBJECT: GRB 210222B: REM observations of the optical/NIR afterglow
DATE:    21/02/25 21:29:46 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <pda.davanzo@gmail.com>

P. D'Avanzo, S. Covino, D. Fugazza, A. Melandri (INAF-OAB) on behalf of the REM team, report:

We observed the field of GRB 210222B (Gropp et al., GCN Circ. 29545) with the REM 60cm robotic telescope 
located at the ESO premise of La Silla (Chile). The observations were performed starting  on 2021 February 23 
at 00:18:20 UT (i.e. 1.68 hours after the burst) and were carried in the g, r, i, z, J and H bands. 

The optical afterglow (Gropp et al., GCN Circ. 29545) is detected in all bands. 

From preliminary photometry we obtain for the optical/NIR afterglow the following magnitudes:

r = 18.85 +/- 0.13 (AB; calibrated against the Pan-STARRS catalogue)
H = 16.39 +/- 0.20 (Vega; calibrated against the 2MASS catalogue)

at a mid time of t-t0 = 1.93 hours.


GRB_name: GRB210226A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29568
SUBJECT: GRB 210226A: Swift detection of a burst
DATE:    21/02/26 05:11:11 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. P. Beardmore (U Leicester), N. J. Klingler (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 04:43:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210226A (trigger=1034721).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 124.138, +57.577 which is 
   RA(J2000) = 08h 16m 33s
   Dec(J2000) = +57d 34' 38"
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 30 sec.  The peak count rate
was ~3400 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 04:45:35.3 UT, 98.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 124.1144, 57.5839 which
is equivalent to:
   RA(J2000)  = 08h 16m 27.46s
   Dec(J2000) = +57d 35' 02.2"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 51 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 (5.24 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2
(+1.84/-1.67) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 101 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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
0.048. 

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: GRB210222B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29569
SUBJECT: GRB 210222B: 1.3m DFOT Optical upper limit
DATE:    21/02/26 06:14:15 GMT
FROM:    Rahul Gupta at ARIES, India  <rahulbhu.c157@gmail.com>

Rahul Gupta, A. Kumar, Dimple, A. Ghosh, A. Aryan, V. Negi, B. Kumar,
S. B. Pandey, and K. Misra (ARIES) report:

We observed the field of Swift detected GRB 210222B (Gropp et al., GCN
29545) with 1.3m Devasthal Fast Optical Telescope (DFOT) located at
Devasthal observatory of Aryabhatta Research Institute of
Observational Sciences (ARIES), India. The observations were started
on 2021-02-23 at ~ 19:15 UT, i.e., ~ 20.6 hours after the BAT trigger.
We have taken multiple frames having an exposure time of 120 s in the
R and I filters.  We stacked the images after the alignment. We did
not detect the optical afterglow reported previously (Gropp et al. GCN
29545; Hu et al. GCN 29546; Strausbaugh et al. GCN 29547; Mong et al.
GCN 29548, 29550; Perley et al. GCN 29549; Zhu et al. GCN 29551,
Fernandez et al. GCN 29552; Lipunov et al. GCN 29554; Jelinek et al.
GCN 29557; Siegel et al. GCN 29559; Gokuldass et al. GCN 29562; Belkin
et al. GCN 29563; and D'Avanzo et al. GCN 29567) in our stacked image.

We obtain the following 3-sigma upper limit in the stacked image.

Date Start_UT T_start-T0 (hour) Filter  Exp time (s)  Limiting magnitude
====================================================
2021-02-23 19:15   ~20.6          R   120*30      > 21.1



The magnitude is not corrected for the Galactic extinction in the
direction of the burst. Photometric calibration is performed using the
standard stars from the USNO-B1.0 catalog.
This circular may be cited.


GRB_name: GRB210226A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29570
SUBJECT: GRB 210226A: Ondrejov BART/SBT optical limit
DATE:    21/02/26 08:05:59 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

Martin Jelinek, Jan Strobl, Rene Hudec and Cyril Polasek (ASU CAS Ondrejov,
CZ), report:

The 0.2 m Small Binocular Telescope (BART/SBT) of Ondrejov observatory in
Czech republic reacted robotically to the alert of GRB 210226A (Beardmore
et al, GCNC 29568), obtaining a series of 12 s unfiltered images starting
at 04:54:55.8 UT, i.e. 659 s post trigger.

We do not detect any new source within the XRT errorbox neither in single
images (3-sigma limit r'(AB) > ~14.0) nor in a combined 30 x 12 s frame
(mean exp time 1033 s post trigger, 3-sigma limit r'(AB) > ~15.8) as
calibrated against the Atlas catalog (Tonry et al. ApJ 867, 105, 2018).


GRB_name: GRB210226A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29571
SUBJECT: GRB 210226A: Enhanced Swift-XRT position
DATE:    21/02/26 12:08:48 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 1421 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 210226A, 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 = 124.11528, +57.58394 which is equivalent
to:

RA (J2000): 08h 16m 27.67s
Dec (J2000): +57d 35' 02.2"

with an uncertainty of 1.5 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: GRB210226A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29572
SUBJECT: GRB 210226A: Burke-Gaffney Observatory optical upper limit
DATE:    21/02/26 15:11:19 GMT
FROM:    Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>

I observed the field of GRB 210226A (Beardmore et al., GCN Circ.
29568) with remote telescope (0.61-m f/6.5 Corrected Dall-Kirkham +
CCD) of Burke-Gaffney Observatory (Halifax, Canada). Image (clear:
without filter) with 180 seconds exposure time was obtained on
2021-02-26. Start time of exposure: 08:00:36 UT (3 h. 16 m. 39 s.
after trigger). I did not detect any optical transients (magnitude
limit of about 18.0). Image available here:
http://www.ap.smu.ca/~bgo/sm/id.php?app=0&id=13614


GRB_name: GRB210218A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29573
SUBJECT: GRB 210218A: Swift-XRT confirmation of afterglow 
DATE:    21/02/26 16:32:25 GMT
FROM:    Boris Sbarufatti at PSU  <bxs60@psu.edu>

B. Sbarufatti (PSU), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team

Swift-XRT has performed follow up observations of GRB 210218A (Sbarufatti et al. GCN Circ. 29529).
The Swift-BAT trigger happened while the burst position in the sky was Moon constrained for XRT and UVOT observations. 
A first follow up observation was performed when the target emerged from Moon constraint, with one uncatalogued X-ray source (source #3) detected inside the BAT error circle (Sbarufatti et al. GCN Circ. 29542).

Swift-XRT observed the field again, for a further 4.7 ks, from T+497 ks to T+549 ks. Source #3 has faded below detection, with a 3-sigma upper limit of  2.5E-3 cts s^-1 (equivalent to  4.6E-14 erg cm^-2 s^-1 ), and is thus confirmed to be the burst afterglow.

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


GRB_name: GRB210226A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29574
SUBJECT: Swift GRB 210226A: Global MASTER-Net observations report 
DATE:    21/02/26 16:46:58 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-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) was pointed to the Swift GRB 210226A ( A. P. Beardmore et al., GCN 29568) errorbox  42015 sec after notice time and 42682 sec after trigger time at 2021-02-26 16:35:20 UT, with upper limit up to  17.3 mag. Observations started at twilight.  The observations began at zenith distance = 30 deg. The sun  altitude  is -13.1 deg. 

The galactic latitude b = 34 deg., longitude l = 160 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1556267

We obtain a following upper limits.  

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

   42773 |      MASTER-Tavrida |   C |   180 | 17.3 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210226A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29575
SUBJECT: GRB 210226A: Swift-XRT refined Analysis
DATE:    21/02/26 18:18:27 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 6.2 ks of XRT data for GRB 210226A (Beardmore et al.
GCN Circ. 29568), from 101 s to 39.3 ks after the  BAT trigger. The
data comprise 12 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Goad et al. (GCN Circ. 29571).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.0 (+0.3, -0.4). At T+423 s  the decay
flattens to an alpha of -0.3 (+0.4, -1.1) before breaking again at
T+1011 s to a final decay with index alpha=1.14 (+0.09, -0.08).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.96 (+0.18, -0.17). The
best-fitting absorption column is  1.9 (+/-0.6) x 10^21 cm^-2, in
excess of the Galactic value of 5.2 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 3.6 x 10^-11 (4.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.9 (+/-0.6) x 10^21 cm^-2
Galactic foreground: 5.2 x 10^20 cm^-2
Excess significance: 4.0 sigma
Photon index:      1.96 (+0.18, -0.17)

If the light curve continues to decay with a power-law decay index of
1.14, the count rate at T+24 hours will be 4.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x
10^-13 (2.1 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/01034721.

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


GRB_name: GRB210226A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29576
SUBJECT: GRB 210226A: KAIT Optical Upper Limit
DATE:    21/02/26 18:29:47 GMT
FROM:    Weikang Zheng at UC Berkeley  <weikang@berkeley.edu>

WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on

behalf of the KAIT GRB team:


The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at

Lick Observatory, responded to Swift GRB 210226A (Beardmore et al.,

GCN 29568) starting at 04:56:15 UT, 738s after the burst.

Observations were performed with an automatic sequence in the

clear (roughly R), V, and I filters, and the exposure time was 20s

per image. We do not detect any optical afterglow candidate within

the enhanced XRT position error circle (Goad et al., GCN 29571),

neither in single image, nor in the co-add images. The typical

limiting magnitude of our single clear image is about 19.0 mag

calibrated to the USNOB1.0 catalog. Our result is consistent with

the optical upper limit reported by other groups (Jelinek et al.,

GCN 29570; Romanov, GCN 29572; Lipunov et al., GCN 29574).


GRB_name: GRB210217A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29577
SUBJECT: GRB 210217A: Mondy optical observations
DATE:    21/02/26 18:35:21 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

N.Pankov (HSE), S. Belkin (IKI),  A. Pozanenko (IKI), E. Klunko (ISTP) 
report  on behalf of IKI GRB FuN:

We observed the field of GRB 210217A (Simpson  et al., GCN  29521) with 
AZT-33IK telescope of Sayan observatory (Mondy)  on 2021-02-19 and XX. 
Within enhanced XRT position (Evans et al., GCN 29525) we do not detect 
afterglow (Simpson  et al., GCNs  29521,29555;  Zhu  et al., GCN  29523; 
Zheng et al., GCN 29533; Shrestha et al., GCN  29535; Kumar et al., GCN 
29539). Preliminary photometry of the filed is following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-02-19 13:10:59   1.58579    R      2190   n/d   n/d   22.2
2021-02-21 16:05:26   3.71250    R      3150   n/d   n/d   22.8
2021-02-19+2021-02-21 2.65193    R      5850   n/d   n/d   22.9

The photometry is based on the nearby USNO-B1.0 star
USNO-B1.0_id R2
1587-088041      17.94

A light curve of afterglow of GRB 210217A (based on published 
photometry) and upper limits can be found in
http://grb.rssi.ru/GRB210217A/GRB210217A_LC.jpg

Using  upper   upper limit we may suggest a possible jet break of the 
light curve we may suggest a jet break between 1.58 and 3.71 days after 
power law decay with index alpha of -0.48 (Shrestha et al., GCN 29535).


GRB_name: GRB210226A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29578
SUBJECT: GRB 210226A: Fermi GBM detection
DATE:    21/02/27 03:20:46 GMT
FROM:    Joshua Wood at MSFC/Fermi-GBM  <joshua.r.wood@nasa.gov>

J. Wood (NASA/MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 04:43:56.56 UT on 26 February 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210226A (trigger 636007441 / 210226197)
which was also detected by the Swift/BAT and Swift/XRT (A.P. Beardmore et al. 2019, GCN 29568).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 58.6 degrees.

The GBM light curve consists of a single peak
with a duration (T90) of about 26 s (50-300 keV).
The time-averaged spectrum from T0-6 s to T0+18 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.2 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 170 +/- 29 keV

The event fluence (10-1000 keV) in this time interval is
(2.7 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.2 s in the 10-1000 keV band
is 4.1 +/- 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: GRB210226A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29579
SUBJECT: GRB 210226A: Swift-BAT refined analysis
DATE:    21/02/27 04:04:47 GMT
FROM:    Sibasish Laha at GSFC  <sibasish.laha@nasa.gov>

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),
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 210226A (trigger #1034721)
(Beardmore, et al., GCN Circ. 29568).  The BAT ground-calculated position is
RA, Dec = 124.153, 57.585 deg which is
   RA(J2000)  =  08h 16m 36.7s
   Dec(J2000) = +57d 35' 06.9"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.

The BAT light curve showed a complex structure with a duration of about ~30 sec.
T90 (15-350 keV) is 20.80 +- 1.68 sec (estimated error including systematics).

The time-averaged spectrum from T-1.92 to T+20.95 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.44 +- 0.15.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+0.02 sec in the 15-150 keV band
is 2.8 +- 0.3 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/1034721/BA/


GRB_name: GRB210225A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29584
SUBJECT: GRB 210225A: Insight-HXMT/HE detection
DATE:    21/02/27 13:29:26 GMT
FROM:    Chao Zheng at IHEP  <zhengchao97@ihep.ac.cn>

C. Zheng, C. Cai, J. C. Liu, Q. Luo, S. Xiao, 
W. C. Xue, Q. B. Yi, Y. Q. Zhang, Y. Huang, C. K. Li, 
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 2021-02-25T05:13:36.00 (T0), Insight-HXMT/HE detected 
GRB 210225A (trigger ID: HEB210225217) in a routine search of the data, 
which also triggered Fermi/GBM (trigger ID: bn210225218).

The Insight-HXMT/HE light curve mainly consists of multiple
pulses with a duration (T90) of 10.65 s measured from T0-0.36 s. 
The 1-ms peak rate, measured from T0-0.558 s, is 921 cnts/sec. 
The total counts from this burst is 7622 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210225217_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: GRB210228A
Detection_method: CALET
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29588
SUBJECT: GRB 210228A: GECAM detection
DATE:    21/02/28 11:46:57 GMT
FROM:    Y Q Zhang at IHEP  <yqzhang@ihep.ac.cn>

Y. Q. Zhang, S. L. Xiong, S. Xiao, C. Cai, Y. Zhao, J. C. Liu,
C. Y. Li, Q. B. Yi, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao, Y. Huang,
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,
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 210228A, at 2021-02-28T06:38:32.600 UTC (denoted as T0),
which was also detected by Fermi/GBM (Trig# 636187116) and
CALET/CGBM (Trig# 1298529456).

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 broad pulse with a duration of about 40 s.  

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: 85.5 deg Dec: -41.8 deg
Err: 2.1 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.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_68193512.png

The GECAM preliminary location could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_skymap_bdm_68193512_V01.png

This burst is temporally and positional coincident with Fermi/GBM trigger
(trig# 636187116).

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: GRB210226A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29590
SUBJECT: GRB 210226A: Swift/UVOT Upper Limits
DATE:    21/02/28 23:29:56 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (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 210226A
102 s after the BAT trigger (Beardmore et al., GCN Circ. 29568).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 29568)
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           102          251          147         >20.9
u_FC               314          563          246         >20.4
white              102         1192          353         >21.4
v                  643         1236           72         >19.1
b                  569         1167           58         >19.9
u                  314         5121          463         >20.5
w1                 692         4935          236         >20.4
m2                4530         4730          197         >20.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.049 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210217A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29591
SUBJECT: GRB 210217A: 3.6m DOT optical observations
DATE:    21/03/01 07:26:44 GMT
FROM:    Dimple Panchal at ARIES, India  <dimplepanchal96@gmail.com>

Dimple (ARIES), K. Misra (ARIES), A. Ghosh (ARIES), R. Gupta (ARIES),  A.
Kumar (ARIES), B. Kumar (ARIES), S.B. Pandey (ARIES) report:

We carried out the follow-up observations of GRB 210217A ( Simpson et al.
GCN #29521) with Aries Devasthal Faint Object Spectrograph and Camera
(ADFOSC) mounted on the 3.6m Devasthal Optical Telescope (DOT) at Devasthal
observatory of Aryabhatta Research Institute of observational sciencES
(ARIES), India.  We detected the optical afterglow (Simpson et al. GCNs
#29521,29555; Zhu et al. GCN #29523; Zheng et al. GCN #29533; Shrestha et
al. GCN #29535; Kumar et al., GCN #29539) at ~ 1.7 days after the burst.

Preliminary photometry is following :

Date               UT start         Filter       Exp. (s)    Mag       err
2021-02-19     15:47:38          r            4*900     22.32      0.17
2021-02-20     16:30:35          r           10*300    >22.60     ----

The reported magnitudes are calibrated with the nearby PanSTARRS field and
are not corrected for Galactic extinction in the direction of the burst.

Using our data along with the data taken from  Zhu et al. GCN #29523; Zheng
et al. GCN #29533; Kumar et al., GCN #29539, we obtain a decay index of
0.47 +-  0.03 consistent with the value quoted by Shrestha et al. # GCN
29535.



.


GRB_name: GRB210228B
Detection_method: IPN Triangulation
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29594
SUBJECT: GRB 210228B: Insight-HXMT/HE detection
DATE:    21/03/05 08:47:07 GMT
FROM:    Wangchen Xue at IHEP  <xuewc@ihep.ac.cn>

W. C. Xue, C. Cai, J. C. Liu, Q. Luo, S. Xiao, 
Q. B. Yi, Y. Q. Zhang, C. Zheng, Y. Huang, C. K. Li, 
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 2021-02-28T01:22:53.900 (T0), Insight-HXMT/HE detected 
GRB 210228B (trigger ID: HEB210228057) in a routine search of the data, 
which also triggered Fermi/GBM (Trig# 635922820) and IPN.

The Insight-HXMT/HE light curve mainly consists of multiple
pulses with a duration (T90) of 1.66 s measured from T0-0.11 s. 
The 1-ms peak rate, measured from T0+0.03 s, is 4418 cnts/sec. 
The total counts from this burst is 2916 counts. 
URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210228057_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: GRB210305A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29595
SUBJECT: GRB 210305A: Swift detection of a burst
DATE:    21/03/05 19:21:53 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC),
N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 19:03:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210305A (trigger=1035922).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 319.814, +34.557 which is 
   RA(J2000) = 21h 19m 15s
   Dec(J2000) = +34d 33' 24"
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 100 sec.  The peak count rate
was ~3200 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 19:04:21.28 UT, 76.8 seconds after
the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with position: RA, Dec 319.80764, 
34.554389 which is equivalent to:
   RA(J2000)  = 21h 19m 13.83s
   Dec(J2000) = +34d 33' 15.8"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 21 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 85 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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
0.155. 

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: GRB210305A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29596
SUBJECT: Swift GRB 210305A: Global MASTER-Net observations report 
DATE:    21/03/06 00:03:16 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 210305A ( A. D'Ai et al., GCN 29595) errorbox  17580 sec after notice time and 17602 sec after trigger time at 2021-03-05 23:56:26 UT, with upper limit up to  16.9 mag. The observations began at zenith distance = 82 deg. The sun  altitude  is -39.6 deg. 

The galactic latitude b = -11 deg., longitude l = 81 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1561780

We obtain a following upper limits.  

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

   17632 |   MASTER-Kislovodsk |   C |    60 | 16.9 |        
   17713 |   MASTER-Kislovodsk |   C |    60 | 16.9 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210306A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29597
SUBJECT: GRB 210306A: Swift detection of a burst with a bright optical counterpart
DATE:    21/03/06 04:12:28 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

V. D'Elia (SSDC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), J. A. Kennea (PSU), N. J. Klingler (PSU),
S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL) and A. Tohuvavohu (U Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 03:53:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210306A (trigger=1035994).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 129.965, +60.196 which is 
   RA(J2000)  =  08h 39m 52s
   Dec(J2000) = +60d 11' 46"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks in a complex
structure with a duration of about 15 sec.  The peak count rate
was ~20,000 counts/sec (15-350 keV), at ~7 sec after the trigger. 

The XRT began observing the field at 03:55:12.07 UT, 74.9 seconds after
the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with a position: RA, Dec 129.96204, 
60.203271 which is equivalent to:
   RA(J2000)  = 08h 39m 50.89s
   Dec(J2000) = +60d 12' 11.7"
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 27 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 http://www.swift.ac.uk/sper. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 85 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 08:39:49.95 = 129.95813
  DEC(J2000) = +60:12:19.4  =  60.20538
with a 90%-confidence error radius of about 0.61 arc sec. This position is 13.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.22 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.052. 

Burst Advocate for this burst is V. D'Elia (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: GRB210306A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29598
SUBJECT: GRB 210306A: DDOTI Afterglow Confirmation
DATE:    21/03/06 04:28:38 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 Swift/BAT GRB 210306A (D'Elia et al., GCN Circ.
29597) with the DDOTI wide-field imager at the Observatorio AstronÃ³mico Nacional
on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) starting at
2021-03-06 04:07 UTC (from 14 minutes after the trigger).

We observed a region covering aproximately 7 degrees in RA and 10 degrees in
declination (about 70 square degrees) centered on the XRT position in the w
filter. We calibrated our images against the APASS catalog.

Compared to the USNO-B1, Pan-STARRS DR1, and APASS DR10 catalogs, we detect a
bright source at 08:39:50.04 +60:12:18.9 (J2000) fading from about w = 17. This
confirms the afterglow reported in UVOT observations by D'Elia et al. (GCN Circ.
29597)

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


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29599
SUBJECT: GRB 210306A: iTelescope optical afterglow observations
DATE:    21/03/06 05:53:48 GMT
FROM:    Filipp Dmitrievich Romanov at Amateur astronomer  <filipp.romanov.27.04.1997@gmail.com>

I observed the field of GRB 210306A (D'Elia et al., GCN Circ. 29597)
with remote telescope T24 (0.61-m f/6.5 reflector + CCD) of
iTelescope.Net in Sierra Remote Observatory (Auberry, California, USA)
on 2021-03-06. Two images (exposures 300 seconds, BINx1) were obtained
with luminance filter since 04:42:56 UT (2939 seconds after the
trigger) and since 04:48:59 UT (3302 seconds after the trigger). I
clearly detected the optical afterglow in UVOT position. The following
magnitudes were measured from comparison to r magnitudes of nearby
stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016): 17.80
(+/- 0.057) and 17.97 (+/- 0.038).

Magnitudes were not corrected for Galactic extinction.

Stacked image available here:
https://www.flickr.com/photos/filipp-romanov/51007330278


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29600
SUBJECT: GRB 210306A: LCO Optical Afterglow Detection
DATE:    21/03/06 07:40:57 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 210306A (D'Elia et al., GCN 29597) with the LCO 1-m Sinistro instrument at the McDonald Observatory, Texas, USA site, on March 6, from 06:49 to 07:06 UT (corresponding to 2.93 to 3.22 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 4x120s exposures in R and I. We clearly detect an optical source in R and I band in stacked images at a location consistent the initial UVOT detection (D'Elia et al., GCN 29597), in agreement with other optical afterglow detections (Watson et al., GCN 29598; Romanov, GCN 29599).  Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:

R = 19.00 +/- 0.02

I = 17.70 +/- 0.03

These magnitudes are not corrected for galactic extinction.  The fainter R magnitude could indicate a moderately high redshift.

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


GRB_name: GRB210306B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29601
SUBJECT: GRB 210306B: Swift detection of a burst
DATE:    21/03/06 09:54:05 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), K. L. Page (U Leicester) and
T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 09:32:14 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210306B (trigger=1036024).  Swift did not slew to the burst
because of Sun constraint.  The BAT on-board calculated location is 
RA, Dec 331.848, +10.175 which is 
   RA(J2000)  = 22h 07m 23s
   Dec(J2000) = +10d 10' 30"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a few peaks
structure with a duration of at least 15 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Due to an observing constraint, Swift will not slew to this target. 
There will be no XRT or UVOT data. 

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: GRB210306A
Detection_method: Fermi LAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29602
SUBJECT: GRB 210306A: Fermi-LAT detection
DATE:    21/03/06 14:19:02 GMT
FROM:    Milena Crnogorcevic at U.of Maryland/NASA-GSFC  <milenaGCN@gmail.com>

M. Ohno (Hiroshima Univ. & Eotvos Univ.), M. Axelsson (KTH &
StockholmUniv.), S. Cutini (INFN Perugia), F. Longo (University & INFN
Trieste), and M. Crnogorcevic (Univ. of Maryland & NASA/GSFC)
report on behalf of the Fermi-LAT Collaboration:

On March 06, 2021, Fermi-LAT detected high-energy emission from GRB
210306A, which was also detected by
Fermi-GBM (trigger 636695642), Swift (D'Elia et al.; GCN 29597), and
confirmed the afterglow by ground telescopes
(M. Watson et al.; GCN 29598, Dmitrievich Romanov; GCN 29599,
Strausbaugh and. Cucchiara; GCN 29600).

The best LAT on-ground location is found to be RA, Dec 130.3, 60.2
(degrees, J2000)
with an error radius of 0.38 deg (90% containment, statistical error only).
This was 10 deg from the LAT boresight at the time of the GBM trigger:

T0 =  03:53:57.11 UT.

The data from the Fermi-LAT show a significant increase
in the event rate after the GBM trigger that is spatially correlated with the
GBM emission (5.8 degrees from the GBM location) with high significance.
The photon flux above 100 MeV in the time interval 0-3000 s after the
GBM trigger is (6.6+/-3.5 e-7) ph/cm2/s.

The estimated photon index above 100 MeV is -2.0(+/-0.4).

The highest-energy photon is a 1.9 GeV event which is observed 790 seconds
after the GBM trigger.

The Fermi-LAT point of contact for this burst is
Milena Crnogorcevic (mcrnogor@astro.umd.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: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29603
SUBJECT: GRB 210306A: iTelescope T24 optical observations
DATE:    21/03/06 14:23:19 GMT
FROM:    Veli-Pekka Hentunen at Taurus Hill Obs,A95  <veli-pekka.hentunen@kassiopeia.net>

Veli-Pekka Hentunen and Markku Nissinen (Taurus Hill Observatory, Varkaus, 

Finland) report:

 

We have detected GRB 210306A optical afterglow using iTelescope T24 

(0.61-m f/6.5 + CCD) telescope in Sierra Remote Observatory  (Auberry, 

California, USA). The observations were started at 2021-03-06 05:02:41 (UT).

We used Luminance filter and 300 sec exposures. 

 

The afterglow was detected at the position RA 08 39 50.11 DEC +60 12 18.8.  

The following magnitudes were measured from comparison of  a nearby star

(r = 16.974) from Pan-STARRS DR1 catalogue (Chambers et al., 2016):

 

Tmid (h:min:sec)+T0    Mag     Mag_err            

01:11:12                      18.08   0.08

01:16:55                      17.97   0.06

01:22:47                      18.13   0.07

02:06:55                      18.41   0.10

02:14:53                      18.44   0.09

02:18:53                      18.52   0.10

02:24:37                      18.63   0.10

03:03:34                      18.82   0.11

03:09:13                      18.85   0.11

03:20:45                      18.87   0.12

03:26:56                      18.91   0.12

03:32:55                      18.84   0.13

04:33:44                      19.33   0.19

04:39:39                      19.22   0.18

05:03:57                      19.33   0.21

05:27:40                      19.61   0.38

 

Magnitudes were not corrected for galactic extinction.

 

URL link for the L filter 300s image:

https://www.kassiopeia.net/2021/03/06/grb-210306a-havainto/


GRB_name: GRB210306A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29604
SUBJECT: GRB 210306A: Tautenburg observations
DATE:    21/03/06 17:15:56 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

B. Stecklum, S. Klose, A. Nicuesa Guelbenzu, S. Melnikov, and S. Hoegner 
(all Tautenburg) report:

We observed the field of GRB 210306A (D'Elia et al., GCN 29597) with the 
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD 
camera.

Between 4:29 UT and 4:48 UT the afterglow was fading from R=17.33 +/- 0.02 
to 17.53 +/- 0.09 mag (Vega), calibrated against the USNO B1 star at R.A., 
Decl. (J2000) = 129.924281, +60.163889 (DS9, R2mag = 15.23) close to the 
afterglow position.


GRB_name: GRB210306A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29605
SUBJECT: GRB 210306A: Fermi GBM observation
DATE:    21/03/06 19:07:36 GMT
FROM:    Peter Veres at UAH  <veresp@gmail.com>

P. Veres (UAH)
reports on behalf of the Fermi GBM Team:

"At 03:53:57.11 UT on 6 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210306A (trigger 636695642 / 210306162).
which was also detected by the Swift/BAT (D'Elia et al., GCN 29597)
and Fermi/LAT (Ohno et al., GCN 29602).
The GBM on-ground location is consistent with the Swift position.


The GBM light curve shows multiple overlapping pulses
with a duration (T90) of about 9.5 s (50-300 keV).
The time-averaged spectrum from T0-0.6 s to T0+11.6 s is
best fit by a Band function with Epeak = 59.4 +/- 2.2 keV,
alpha = -0.60 +/- 0.08, and beta = -2.53 +/- 0.06.

The event fluence (10-1000 keV) in this time interval is
(9.82 +/- 0.20)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+7.6 s in the 10-1000 keV band
is 26.6 +/- 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: GRB210306A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29606
SUBJECT: Swift GRB 210306A: Global MASTER-Net observations report 
DATE:    21/03/06 20:02:39 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) was pointed to the Swift GRB 210306A ( V. D'Elia et al., GCN 29597) errorbox  57322 sec after notice time and 57335 sec after trigger time at 2021-03-06 19:49:32 UT, with upper limit up to  20.0 mag. The observations began at zenith distance = 17 deg. The sun  altitude  is -42.8 deg. 

The galactic latitude b = 37 deg., longitude l = 157 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1562037

We obtain a following upper limits.  

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

   30222 |             MASTER- |   C |    60 | 18.5 |        
   31162 |             MASTER- |   C |    60 | 18.4 |        
   32113 |             MASTER- |   C |    60 | 18.9 |        
   57426 |      MASTER-Tavrida |   C |   180 | 20.0 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29607
SUBJECT: GRB 210306A: NEXT optical observations
DATE:    21/03/07 04:10:04 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210306A (D'Elia et al., GCN 29597) using 
the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. 
Observations started at 16:11:33 UT on 2021-03-06, i.e., 12.29 hr after 
the BAT trigger. We obtained 15x200 s frames in the Sloan r-filter.

The previously reported optical afterglow (e.g., D'Elia et al., GCN 
29597; Watson et al., GCN 29598; Romanov F., GCN 29599; Strausbaugh et 
al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et al., GCN 29604) 
is clearly detected in our stacked image, with r = 21.0 +/- 0.1 mag at 
12.76 hr post-burst, calibrated with nearby PS1 stars.


GRB_name: GRB210306A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29608
SUBJECT: GRB 210306A: MITSuME Akeno optical observation
DATE:    21/03/07 06:38:39 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

R. Hosokawa, R. Adachi, K. L. Murata, M. Niwano, F. Ogawa, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210306A (D'Elia et al. GCN #29597, Watson
et al. GCN 29598, Romanov GCN #29599, Strausbaugh et al. GCN #29600,
Ohno et al. GCN #29602, Hentunen et al. GCN #29603, Stecklum et al.
GCN #29604, Veres et al. GCN #29605, Lipunov et al. GCN #29606, Zhu et
al. GCN #29607) 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 2021-03-06 09:12:03 UT (5.3 hours after Swift BAT trigger).
We stacked the images with good conditions. We marginally detected the
point source at the position consistent with the afterglow detected
previously(D'Elia et al. GCN #29597, Watson et al. GCN 29598, Romanov
GCN #29599, Strausbaugh et al. GCN #29600, Hentunen et al. GCN #29603,
Stecklum et al. GCN #29604, Zhu et al. GCN #29607).
We measured the magnitudes as follows.

T0+[hour] MID-UT T-EXP[sec] measured magnitudes
------------------------------------------------------------------------------------------------
5.3 11:38:10 8160 g'=20.0+/-0.4, Rc=20.2+/-0.4, Ic=19.0+/-0.3
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
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: GRB210307A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29610
SUBJECT: GRB 210307A: Swift detection of a burst
DATE:    21/03/07 09:04:30 GMT
FROM:    Elena Ambrosi at INAF-IASF  <elena.ambrosi@inaf.it>

E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), N. J. Klingler (PSU), K. L. Page (U Leicester)
and T. Sakamoto (AGU) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 08:42:38 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210307A (trigger=1036139).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 119.190, -66.963 which is 
   RA(J2000) = 07h 56m 46s
   Dec(J2000) = -66d 57' 45"
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 120 sec.  The peak count rate
was ~1300 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 96.2 s seconds after
the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with a position: RA, Dec 119.239583, 
-66.969694 which is equivalent to: 
   RA(J2000)  = 07 56 57.5
   Dec(J2000) = -66 58 10.9 
with an uncertainty of 4.7 arcseconds (radius, 90% containment). This
location is 73.8 arcsec 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 http://www.swift.ac.uk/sper. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 100 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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
0.138. 

This source lies within the current (Sector 35) field-of-view of TESS camera 4. 

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: GRB210305A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29611
SUBJECT: GRB 210305A: Swift-BAT refined analysis
DATE:    21/03/07 13:13:21 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
A. D'Ai (INAF-IASFPA), S. Laha (GSFC/UMBC), 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 210305A (trigger #1035922)
(D'Ai, et al., GCN Circ. 29595).  The BAT ground-calculated position is
RA, Dec = 319.808, 34.548 deg which is
    RA(J2000)  =  21h 19m 13.9s
    Dec(J2000) = +34d 32' 52.8"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 74%.
  
The BAT light curve showed a complex structure with a duration of about ~100 sec.
T90 (15-350 keV) is 68.6 +- 4.4 sec (estimated error including systematics).
  
The time-averaged spectrum from T-21.65 to T+71.76 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.93 +- 0.19,
and Epeak of 104.1 +- 19.7 keV (chi squared 43.93 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 7.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.26 sec in the 15-150 keV band is
3.4 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.49 +- 0.04 (chi squared 71.71 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/1035922/BA/


GRB_name: GRB210306B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29612
SUBJECT: GRB 210306B: Swift-BAT refined analysis
DATE:    21/03/07 13:14:21 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), S. Laha (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-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210306B (trigger #1036024)
(D'Ai, et al., GCN Circ. 29601).  The BAT ground-calculated position is
RA, Dec = 331.813, 10.152 deg which is
    RA(J2000)  =  22h 07m 15.1s
    Dec(J2000) = +10d 09' 06.8"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 21%.
  
The BAT light curve showed a multi-peaked structure that starts at T-2 s and
ends at ~T+25 s. T90 (15-350 keV) is 24.32 +- 2.45 sec (estimated error
including systematics).
  
The time-averaged spectrum from T-2.42 to T+24.63 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.38 +- 0.20.  The fluence in the 15-150 keV band is 1.7 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.04 sec in the 15-150 keV band
is 2.4 +- 0.5 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/1036024/BA/


GRB_name: GRB210307A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29613
SUBJECT: GRB 210307A: LCO Optical Upper Limits
DATE:    21/03/07 13:44:16 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 210307A (Ambrosi et al., GCN 29610) with the LCO 1-m Sinistro instrument at the Sutherland Observatory, South Africa site, on March 7, from 09:28 to 09:59 UT (corresponding to 0.60 to 1.18 hours from the GRB trigger time) with the Bessel R and I filters.

We performed a series of 4x240s exposures in R and I. We do not detect an uncatalogued optical source in either band in single frames, or in stacked images at a location consistent the initial XRT detection (Ambrosi et al., GCN 29610).  Using the USNO-B.1 catalog as reference, we calculate the following upper limits:

R > 20.72

I > 20.66

These magnitudes are not corrected for galactic extinction.

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


GRB_name: GRB210307B
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29614
SUBJECT: GRB 210307B: GECAM detection
DATE:    21/03/07 15:29:58 GMT
FROM:    QiBin Yi at IHEP, HXMT  <yiqb@ihep.ac.cn>

Q. B. Yi, S. L. Xiong, S. Xiao, C. Cai, Y. Zhao, J. C. Liu,
C. Y. Li, Y. Q. Zhang, W. C. Xue, C. Zheng, Z. W. Guo, X. Y. Zhao, Y. Huang,
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,
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 short burst,
GRB 210307B, at 2021-03-07T05:56:39.100 UTC (denoted as T0),
which was also detected by INTEGRAL/SPI-ACS (Trig# 9040).

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 0.5 s.  

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: 125.6 deg Dec: 17.5 deg
Err: 7.3 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.

The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_68795799.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: GRB210305A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29615
SUBJECT: GRB 210305A: Swift/UVOT Upper Limits
DATE:    21/03/07 19:43:36 GMT
FROM:    Alexander Belles at PSU/Swift  <aub1461@psu.edu>

A. Belles (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 210305A
85 s after the BAT trigger (D'Ai et al., GCN Circ. 29595).
No optical afterglow consistent with the XRT position
(D'Ai et al. GCN Circ. 29595)
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            86          235          147         >20.19
u_FC               298          548          245         >19.54
white              577         1721          264         >20.51
v                  627         1771          134         >18.55
b                  553         1696          116         >19.37
u                  700         1672           97         >18.86
w1                 676         1818          134         >18.70
m2                 651         1795          136         >18.63
w2                 603         1746          136         >18.60

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.155 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29616
SUBJECT: GRB 210306A: Mondy optical observations
DATE:    21/03/07 20:21:30 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) 
report  on behalf of GRB IKI FuN:

We observed the field of GRB 210306A (D'Elia et al., GCN 29597; Ohno et 
al., GCN 29602) with AZT-33IK telescope of Sayan observatory (Mondy) 
starting on 2021-03-06  (UT) 14:50:30. The optical afterglow (D'Elia et 
al., GCN 29597; Watson et al., GCN 29598; Romanov, GCN 29599; 
Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et 
al., GCN 29604; Lipunov et al. GCN 29606, Zhu et al. GCN 29607; Hosokawa 
et al., GCN  29608) is clearly detected in a combined image. Preliminary 
photometry of the object in a combined image is following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-06 14:50:30   0.47677    R      30*120  20.48 0.05  22.0

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1501-0181731 15.23
1502-0183049 17.69
1501-0181697 17.1


GRB_name: GRB210306A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29617
SUBJECT: GRB 210306A: Swift-BAT refined analysis
DATE:    21/03/07 22:03:13 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
V. D'Elia (SSDC), 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-240 to T+600 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210306A (trigger #1035994)
(D'Elia, et al., GCN Circ. 29597).  The BAT ground-calculated position is
RA, Dec = 129.964, 60.203 deg which is
    RA(J2000)  =  08h 39m 51.3s
    Dec(J2000) = +60d 12' 11.5"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.
  
The BAT light curve showed a complex structure with a duration of about ~10 sec.
T90 (15-350 keV) is 9.12 +- 0.31 sec (estimated error including systematics).
  
The time-averaged spectrum from T-0.18 to T+13.16 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.16 +- 0.19,
and Epeak of 58.4 +- 3.9 keV (chi squared 59.11 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 5.7 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+7.50 sec in the 15-150 keV band is
20.9 +- 0.7 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.91 +- 0.04 (chi squared 111.38 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/1035994/BA/


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29618
SUBJECT: GRB 210306A: 1.3m DFOT observations
DATE:    21/03/08 06:40:03 GMT
FROM:    Dimple Panchal at ARIES, India  <dimplepanchal96@gmail.com>

Dimple (ARIES), A. Ghosh (ARIES), G. Singh (ARIES), R. Gupta (ARIES), A.
Kumar (ARIES), K. Misra (ARIES), S.B. Pandey (ARIES) report:

We observed the afterglow of the GRB 210306A (D'Elia et al. GCN
#29597, Watson et al. GCN 29598, Romanov GCN #29599, Strausbaugh et
al. GCN #29600, Ohno et al. GCN #29602, Hentunen et al. GCN #29603,
Stecklum et al. GCN #29604, Veres et al. GCN #29605, Lipunov et al.
GCN #29606, Zhu et al. GCN #29607)  with 1.3m Devasthal Fast Optical
Telescope (DFOT) at Devasthal observatory of Aryabhatta Research
Institute of observational sciencES (ARIES), India. We took
observations in B,V,R,I bands. We detect the optical afterglow with a
magnitude of 20.24 +- 0.13 in R-band at 9.8 hrs after the burst.
Further observations are ongoing with 1.3m DFOT.

The magnitude is not corrected for the Galactic extinction in the
direction of the burst. The photometric calibration is performed using
the standard stars from the USNO-B1.0 catalog.


GRB_name: GRB210308A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29619
SUBJECT: GRB 210308A: Swift detection of a burst with an optical counterpart
DATE:    21/03/08 06:49:21 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

V. D'Elia (SSDC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),
A. D'Ai (INAF-IASFPA), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
K. L. Page (U Leicester), T. Sakamoto (AGU), M. H. Siegel (PSU) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 06:37:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210308A (trigger=1036227).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 67.088, +37.411 which is 
   RA(J2000)  =  04h 28m 21s
   Dec(J2000) = +37d 24' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a few overlapping peaks
with a duration of about 15 sec.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 06:39:21.81 UT, 85.0 seconds after
the BAT trigger. Using promptly downlinked data we find an
uncatalogued X-ray source with a position: RA, Dec 67.076417, 
37.435310 which is equivalent to:
   RA(J2000)  = 04h 28m 18.34s
   Dec(J2000) = +37d 26' 07.11"
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This
location is 94 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 http://www.swift.ac.uk/sper. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 94 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  = 04:28:17.73 =  67.07388
  DEC(J2000) = +37:26:02.0  =  37.43388
with a 90%-confidence error radius of about 0.63 arc sec. This position is 8.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.57 with a 1-sigma error of about  0.15. No correction has been made for the
expected extinction corresponding to E(B-V) of 1.295. 

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: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29620
SUBJECT: GRB 210306A: continued Mondy optical observations
DATE:    21/03/08 11:16:12 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) 
report  on behalf of GRB IKI FuN:

We continue observations (Belkin et al., GCN 29616)  the field of GRB 
210306A (D'Elia et al., GCN 29597; Ohno et al., GCN 29602) with AZT-33IK 
telescope of Sayan observatory (Mondy). The optical afterglow (D'Elia et 
al., GCN 29597; Watson et al., GCN 29598; Romanov, GCN 29599; 
Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et 
al., GCN 29604; Lipunov et al. GCN 29606, Zhu et al. GCN 29607; Hosokawa 
et al., GCN  29608; Dimple et al., GCN 29618) is still detected in a 
combined image. Preliminary photometry of the afterglow in the combined 
image is following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-07 13:43:24   1.41281    R      5*120  22.09 0.25  22.1

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1501-0181731 15.23
1502-0183049 17.69
1501-0181697 17.1


GRB_name: GRB210308A
Detection_method: MITSuME
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29621
SUBJECT: GRB 210308A: MITSuME Okayama optical upper limits
DATE:    21/03/08 13:51:21 GMT
FROM:    Ryohei Hosokawa at Tokyo Institute of Technology  <hosokawa@hp.phys.titech.ac.jp>

S. Ogata, R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, F. Ogawa,
N. Nakamura, N. Ito, H. Takamatsu, H. Hara, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:

We observed the field of GRB 210308A (D'Elia et al.,GCN Circular
#29619) with the optical three color (g', Rc, and Ic) CCD cameras
attached to the MITSuME 50 cm telescope of Okayama Astrophysical
Observatory, Okayama, Japan. The observation with a series of 60 sec
exposures started at 2021-03-08 11:03:59 UT.(4.5 hours after Swift BAT
trigger) We stacked the images with good conditions. We did not detect
the optical afterglow reported previously (D'Elia et al.,GCN Circular
#29619) 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
------------------------------------------------------------------------------------------------
4.5 11:51:53 4440 g'>17.6, Rc>17.8, Ic>17.8
------------------------------------------------------------------------------------------------
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: GRB210306A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29622
SUBJECT: GRB 210306A: Swift-XRT refined Analysis
DATE:    21/03/08 16:08:27 GMT
FROM:    Valerio D'Elia at ASDC  <valerio.delia@ssdc.asi.it>

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

We have analysed 10 ks of XRT data for GRB 210306A (D'Elia et al. GCN
Circ. 29597), from 65 s to 182.6 ks after the  BAT trigger. The data
comprise 576 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. Using 3375 s of PC mode data and 9 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 = 129.95774, +60.20523
which is equivalent to:

RA (J2000): 08h 39m 49.86s
Dec(J2000): +60d 12' 18.8"

with an uncertainty of 1.4 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.435 (+/-0.027), followed by a break at T+1548 s to an
alpha of 1.58 (+/-0.06).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.89 (+0.05, -0.04). The
best-fitting absorption column is  1.53 (+0.15, -0.14) x 10^21 cm^-2,
in excess of the Galactic value of 4.2 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.98 (+0.14, -0.13)
and a best-fitting absorption column of 1.7 (+/-0.4) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.5 x 10^-11 (4.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.7 (+/-0.4) x 10^21 cm^-2
Galactic foreground: 4.2 x 10^20 cm^-2
Excess significance: 5.2 sigma
Photon index:      1.98 (+0.14, -0.13)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01035994.

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


GRB_name: GRB210308A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29623
SUBJECT: GRB 210308A: Nanshan/NEXT optical upper limits
DATE:    21/03/08 16:27:50 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

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

We observed the field of GRB 210308A (D'Elia et al., GCN 29619) using 
the NEXT-0.6m optical telescope located at Nanshan, Xinjiang, China. 
Observations started at 14:16:29 UT on 2021-03-08, i.e., 7.67 hr after 
the BAT trigger. We obtained 15x200 s frames in the Sloan r- and i- 
bands, respectively.

The optical afterglow (D'Elia et al., GCN 29619) of the burst is not 
detected in our stacked images, down to limiting magnitudes of r ~ 21.7 
and i ~ 21.3, calibrated with nearby PS1 stars.


GRB_name: GRB210307A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29624
SUBJECT: GRB 210307A: Swift-XRT refined Analysis
DATE:    21/03/08 16:42:03 GMT
FROM:    Elena Ambrosi at INAF-IASF  <elena.ambrosi@inaf.it>

A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and E.
Ambrosi (INAF-IASFPA) report on behalf of the Swift-XRT team:

We have analysed 7.0 ks of XRT data for GRB 210307A (Ambrosi et al. GCN
Circ. 29610), from 97 s to 40.0 ks after the  BAT trigger. The data
comprise 149 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. Using 2981 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 =
119.23831, -66.97092 which is equivalent to:

RA (J2000): 07h 56m 57.19s
Dec(J2000): -66d 58' 15.3"

with an uncertainty of 1.5 arcsec (radius, 90% confidence). 

The light curve can be modelled with a series of power-law decays
followed 
by a plateau. The initial decay index is alpha= : 2.11 (+0.10, -0.11).
At T= T0+242.1 s the decay index is alpha=7.88 (+0.12, -2.58) before
breaking again at T=T0+280.5 s with an index alpha= 3.2 (+0.6, -0.4).
After T>T0+10^4 s the lightcurve is in a long lasting plateau phase.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.520 (+0.035, -0.026). The
best-fitting absorption column is  consistent with the Galactic value
of 1.4 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.75 (+0.16, -0.14) and a best-fitting absorption
column of 1.75 (+0.61, -0.30) x 10^21 cm^-2. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.0 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.75 (+0.61, -0.30) x 10^21 cm^-2
Galactic foreground: 1.4 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.75 (+0.16, -0.14)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01036139.

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


GRB_name: GRB210305A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29625
SUBJECT: GRB 210305A: Swift-XRT refined Analysis
DATE:    21/03/08 16:48:20 GMT
FROM:    Antonino D'Ai at IASF-PA  <antonino.dai@inaf.it>

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

We have analysed 11 ks of XRT data for GRB 210305A (D'Ai et al. GCN
Circ. 29595), from 67 s to 178.1 ks after the  BAT trigger. The data
comprise 184 s in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. Using 2502 s of PC mode data and 4 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 = 319.81054, +34.55403
which is equivalent to:

RA (J2000): 21h 19m 14.53s
Dec(J2000): +34d 33' 14.5"

with an uncertainty of 1.4 arcsec (radius, 90% confidence).

The late-time light curve (from T0+5.3 ks) can be modelled with a
power-law decay with a decay index of alpha=0.91 (+0.10, -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.44 (+/-0.08). The
best-fitting absorption column is  3.2 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 2.0 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.84 (+/-0.16) and a
best-fitting absorption column of 4.0 (+0.9, -0.8) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.3 x 10^-11 (6.1 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      4.0 (+0.9, -0.8) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^21 cm^-2
Excess significance: 4.1 sigma
Photon index:      1.84 (+/-0.16)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01035922.

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


GRB_name: GRB210308A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29626
SUBJECT: GRB 210308A: Fermi GBM detection
DATE:    21/03/08 20:27:21 GMT
FROM:    Stephen Lesage at Fermi-GBM Team  <sjl0014@uah.edu>

S. Lesage (UAH), A. von Kienlin (MPE), C. Meegan (UAH), and C. Malacaria
(NASA-MSFC/USRA)
report on behalf of the Fermi GBM Team:

"At 06:37:56.91 UT on 08 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210308A (trigger 636878281 / 210308276)
which was also detected by the Swift/BAT and Swift/XRT
(D'Elia et al. 2021, GCN 29619).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 26
degrees.

The GBM light curve shows a single-peaked structure
with a duration (T90) of about 5.4 s (50-300 keV).
The time-averaged spectrum from T0-1.7 s to T0+7.5 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.82 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 142 +/- 5 keV.
A Band function fits the spectrum equally well with
Epeak = 135 +/- 7 keV, alpha = -0.78 +/- 0.05 and beta = -3.0 +/- 0.4.

The event fluence (10-1000 keV) in this time interval is
(6.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.1 s in the 10-1000 keV band
is 20.0 +/- 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: GRB210308A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29627
SUBJECT: Swift GRB 210308A: Global MASTER-Net observations report 
DATE:    21/03/08 22:18:11 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-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 210308A ( V. D'Elia et al., GCN 29619) errorbox  40899 sec after notice time and 40918 sec after trigger time at 2021-03-08 17:59:54 UT, with upper limit up to  13.9 mag. Observations started at twilight.  The observations began at zenith distance = 74 deg. The sun  altitude  is -12.2 deg. 

MASTER-IAC robotic telescope  located in Spain (IAC Teide Observatory) was pointed to the Swift GRB 210308A errorbox  55958 sec after notice time and 55976 sec after trigger time at 2021-03-08 22:10:53 UT, with upper limit up to  18.5 mag. The observations began at zenith distance = 48 deg. The sun  altitude  is -40.8 deg. 

The galactic latitude b = -7 deg., longitude l = 164 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1563625

We obtain a following upper limits.  

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

   21950 |             MASTER- |   C |    60 | 18.0 |        
   22210 |             MASTER- |   C |    60 | 15.8 |        
   22945 |             MASTER- |   C |    60 | 12.6 |        
   41008 |         MASTER-SAAO |   C |   180 | 13.9 |        
   56067 |          MASTER-IAC |   C |   180 | 18.5 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210305A
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29628
SUBJECT: GRB 210305A: Fermi GBM observation
DATE:    21/03/08 22:42:28 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 19:02:59.40 UT on 05 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210305A (trigger 636663784 / 210305794),
which was also detected by the Swift/BAT/XRT (D'Ai et al., GCN 29595).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 90 degrees.

The GBM light curve shows multiple overlapping pulses
with a duration (T90) of about 61.7 s (50-300 keV).
The time-averaged spectrum from T0-11.3 s to T0+59.4 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.17 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 98 +/- 3 keV.

A Band function fits the spectrum equally well
with Epeak= 95 +/- 4 keV, alpha = -0.11 +/- 0.11 and beta = -3.25 +/- 0.45.

The event fluence (10-1000 keV) in this time interval is
(9.4 +/- 0.2)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.3 s in the 10-1000 keV band
is 4.6 +/- 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: GRB210307A
Detection_method: Swift-UVOT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29629
SUBJECT: GRB 210307A: Swift/UVOT Upper Limits 
DATE:    21/03/08 23:38:27 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>

M. H. Siegel (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 210307A
100 s after the BAT trigger (Ambrosi et al., GCN Circ. 29610).
No optical afterglow consistent with the XRT position
(Ambrosi et al. GCN Circ. 29610)
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           100          250          147         >20.9
u_FC               313          562          246         >20.6
white              100          786          186         >21.1
v                  642          836           39         >19.3
b                  568          761           39         >19.9
u                  313          736          265         >20.6
w1                 692          711           19         >19.6
m2                 667          687           19         >18.7
w2                 618          812           39         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.138 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210308A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29630
SUBJECT: GRB 210308A: Swift/UVOT Detection
DATE:    21/03/09 01:16:01 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

 GRB 210308A: Swift/UVOT Detection

J. D. Gropp (PSU) and V. D'Elia (SSDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210308A
95 s after the BAT trigger (D'Elia et al., GCN Circ. 29619).
A source consistent with the XRT position
(D'Elia et al., GCN Circ. 29619)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  04:28:17.73 =  67.07389 (deg.)
    Dec (J2000) = +37:26:02.1  =  37.43391 (deg.)
with an estimated uncertainty of 0.46 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

b                       765            1189            38        >18.62
uvm2                864            1115            38        >17.52
u                       338            1164          284        >19.50
v                       667            1090            58        >17.84
uvw1               1120            1140            19        >17.25
uvw2                 815            1231            50        >17.91
white                 126             275           292
18.54+-0.07
white                 618            1213          205        >20.20

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.296 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210307A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29632
SUBJECT: GRB 210307A: Swift-BAT refined analysis
DATE:    21/03/09 03:07:58 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

C. B. Markwardt (GSFC), E. Ambrosi (INAF-IASFPA), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), 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-239 to T+700 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210307A (trigger #1036139)
(Ambrosi, et al., GCN Circ. 29610).  The BAT ground-calculated position is
RA, Dec = 119.244, -66.965 deg which is
    RA(J2000)  =  07h 56m 58.5s
    Dec(J2000) = -66d 57' 54.3"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.
  
The mask-weighted light curve shows two isolated peaks.  The initial peak starts
at T-30 sec, peaks at T0 and ends at T+40 sec.  The second peak starts at
T+110 sec, peaks at T+118 sec and ends at T+150 sec.  T90 (15-350 keV) is
262 +- 83 sec (estimated error including systematics).

The time-averaged spectrum from T-159.61 to T+174.53 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.56 +- 0.16.  The fluence in the 15-150 keV band is 2.8 +- 0.3 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.27 sec in the 15-150 keV band
is 1.0 +- 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/1036139/BA/


GRB_name: GRB210308A
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29633
SUBJECT: GRB 210308A: Swift-BAT refined analysis
DATE:    21/03/09 03:09:52 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
V. D'Elia (SSDC), 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-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210308A (trigger #1036227)
(D'Elia, et al., GCN Circ. 29619).  The BAT ground-calculated position is
RA, Dec = 67.083, 37.429 deg which is
    RA(J2000)  =  04h 28m 19.9s
    Dec(J2000) = +37d 25' 42.9"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 32%.
  
The mask-weighted light curve shows a double-peaked structure from T-0.5 sec
to T+9 sec.  The first pulse peaks at T+0.2 sec, and the second pulse peaks
at T+3 sec.  T90 (15-350 keV) is 5.3 +- 0.6 sec (estimated error including systematics).
  
The time-averaged spectrum from T-0.04 to T+7.36 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.76 +- 0.28,
and Epeak of 113.6 +- 31.0 keV (chi squared 52.89 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.2 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+2.12 sec in the 15-150 keV band is
13.6 +- 0.7 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.38 +- 0.06 (chi squared 69.63 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/1036227/BA/


GRB_name: GRB210308A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29634
SUBJECT: GRB 210308A: Mondy and AbAO optical observations
DATE:    21/03/09 06:13:56 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), N. Pankov (HSE), A. Pozanenko (IKI), E. Klunko (ISTP), 
R. Ya. Inasaridze (AbAO), V. R. Ayvazian (AbAO),  G. V. Kapanadze 
(AbAO), D. G. Datashvili (AbAO) report on behalf of IKI-GRB-FuN:

We observed the field of  GRB 210308A (D'Elia et al., GCN 29619) with 
AZT-33IK telescope of Sayan observatory (Mondy) starting on  2021-03-08 
(UT) 13:00:45 and AS-32 telescope of Abastumani observatory (AbAO) 
starting on  2021-03-08 (UT) 16:32:07 (both in R-filter). The optical 
afterglow (D'Elia et al., GCN 29619; Gropp et al., GCN 29630; see also 
Ogata et al., GCN 29621; Zhu et al., GCN 29623; Lipunov et al., GCN 
29627) is detected in stacked image of AZT-33IK and not detected at AS-32.

Date       UT start   t-T0    Filter  Exp.   OT    Err.  UL(3sigma)
                        (mid, days)     (s)

2021-03-08 13:00:45   0.27626  R      15*120 22.77  0.27 22.8 AZT-33IK
2021-03-08 16:32:07   0.42131  R      25*60  n/d    n/d  21.8 AS-32

The photometry is based on nearby USNO-B1.0 stars
USNO-B1.0_id R2
1274-0090800 15.34
1274-0090824 17.35


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29635
SUBJECT: GRB 210306A: continued Mondy optical observations
DATE:    21/03/09 06:31:50 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI),  A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) 
report  on behalf of GRB IKI FuN:

We continue observations (Belkin et al., GCNs 29616,29620)  the field of 
GRB 210306A (D'Elia et al., GCN 29597; Ohno et al., GCN 29602) with 
AZT-33IK telescope of Sayan observatory (Mondy). The optical afterglow 
(D'Elia et al., GCN 29597; Watson et al., GCN 29598; Romanov, GCN 29599; 
Strausbaugh et al., GCN 29600; Hentunen et al., GCN 29603; Stecklum et 
al., GCN 29604; Lipunov et al. GCN 29606, Zhu et al. GCN 29607; Hosokawa 
et al., GCN  29608; Dimple et al., GCN 29618) is detected in a combined 
image. Preliminary photometry of the afterglow in the combined image is 
following

Date       UT start   t-T0       Filter Exp.    OT    Err.  UL(3sigma)
                       (mid, days)        (s)

2021-03-08 13:47:43   2.43317    R      30*120  22.68 0.18  22.9

The photometry is based on the nearby USNO-B1.0 stars
USNO-B1.0_id R2
1501-0181731 15.23
1502-0183049 17.69
1501-0181697 17.11


GRB_name: GRB210306A
Detection_method: Swift-UVOT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29636
SUBJECT: GRB 210306A: Swift/UVOT Detection
DATE:    21/03/09 14:05:28 GMT
FROM:    Kira Simpson at PSU  <kira.simpson1984@gmail.com>

GRB 210306A: Swift/UVOT Detection

K. K. Simpson (PSU) and V. D'Elia (SSDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210306A
85 s after the BAT trigger (D'Elia et al., GCN Circ. 29597).
A source consistent with the XRT position
(D'Elia et al. GCN Circ. 29597)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  08:39:49.98 = 129.95824 (deg.)
    Dec (J2000) = +60:12:19.2  =  60.20533 (deg.)
with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence).

Preliminary detections 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               85          235          147         16.23 +/- 0.03
v                  628          648           20         17.42 +/- 0.24
b                  553          573           20         17.32 +/- 0.13
u                  297          547          246         16.86 +/- 0.04

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.052 in the direction of the burst
(Schlegel et al. 1998).


GRB_name: GRB210306B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29637
SUBJECT: GRB 210306B: Fermi GBM detection
DATE:    21/03/09 17:13:46 GMT
FROM:    Stephen Lesage at Fermi-GBM Team  <sjl0014@uah.edu>

S. Lesage (UAH), A. von Kienlin (MPE), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 09:32:14.42 UT on 06 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210306B (trigger 636715939 / 210306397)
which was also detected by the Swift/BAT (Ambrosi et al. 2021, GCN 29601).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 37
degrees.

The GBM light curve shows a single-peaked structure
with a duration (T90) of about 15 s (50-300 keV).
The time-averaged spectrum from T0-1.3 s to T0+14.1 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.0 +/- 0.2 and
the cutoff energy, parameterized as Epeak, is 73 +/- 8 keV.

The event fluence (10-1000 keV) in this time interval is
(1.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.0 s in the 10-1000 keV band
is 2.7 +/- 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: GRB210306A
Detection_method: correction
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29638
SUBJECT: GRB 210306A: Early Spectroscopy of the Optical Afterglow
DATE:    21/03/09 18:35:39 GMT
FROM:    Paul S. Smith at Steward Observatory  <psmith@as.arizona.edu>

P.S. Smith, Z. Chen, P. Milne, D. Sand, N. Smith, D. Stark, and G.G.
Williams (Steward Observatory, University of Arizona)

Observations of the optical counterpart of GRB 210306A using the B&C
Spectrograph and the University of Arizona, Steward Observatory 2.3m Bok
Telescope located on Kitt Peak, Arizona began at 07:07:50 on March 6, 2021
UTC and ended at 08:23:13 UT.  Three, 1500 s exposures were obtained
centered at 3.384, 3.859, and 4.279 hours after the Swift/BAT detection of
the burst (DElia et al.; GCN Circ. 29597).  Comparison with a
spectrophotometric standard star observed immediately after the optical
afterglow observations suggest that the counterpart was at an approximate
V magnitude of 19.18, 19.33, and 19.46 for the three exposures,
respectively. All spectra show a featureless blue continuum from 350-760nm.
A fit to the least noisy portion (450-750nm) of the scaled median spectrum
from the three observations yields a slope of about -1.25 in log(F_lambda)
vs. log(wavelength). No corrections for Galactic extinction and reddening
have been made.


GRB_name: GRB171205A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29640
SUBJECT: GRB 171205A: Continued ATCA observations
DATE:    21/03/10 08:47:32 GMT
FROM:    James Leung at U of Sydney/VAST  <jleu9465@uni.sydney.edu.au>

James Leung (University of Sydney/CSIRO), Emil Lenc (CSIRO), Tara
Murphy (University of Sydney), Giancarlo Ghirlanda (INAF/Brera),
Ziteng Wang (University of Sydney/CSIRO)

We have been monitoring the late-time radio emission of GRB 171205A
(V. Dâ€™Elia et al., GCN Circ. 22177) centred on the optical
counterpart position (L. Izzo et al., GCN Circ. 22180) with the
Australia Telescope Compact Array (ATCA). The observations took place
on 2021 March 7 (1171 days or 3.21 years post-trigger) at 2.1, 5.5
and 9.0 GHz frequencies. We report the detections below:

Date (UTC) | Freq (GHz) | Peak Flux Density (micro-Jy/beam)
-----------------------------------------------------------
2021/03/07 | 2.1        | 554 +/- 92
2021/03/07 | 5.5        | 293 +/- 35
2021/03/07 | 9.0        | 179 +/- 28

Ongoing observations are planned. 

We thank CSIRO staff for supporting these observations during these
especially difficult times.


GRB_name: GRB210305A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29641
SUBJECT: Konus-Wind detection of GRB 210305A
DATE:    21/03/10 10:04:15 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

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

The long-duration GRB 210305A
(Swift-BAT detection: D'Ai et al., GCN 29595, Krimm et al., GCN 29611;
Fermi-GBM observation: Veres et al., GCN 29628)
triggered Konus-Wind at T0=68578.330 s UT (19:02:58.330).

The burst light curve shows a multipeaked structure
which starts at ~T0-20 s and has the total duration of ~78 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/GRB210305_T68578/

As observed by Konus-Wind, the burst
had a fluence of 1.63(-0.31,+0.43)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+4.224 s,
of 1.23(-0.51,+0.51)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+57.600 s)
is best fit in the 20 keV - 1 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.33(-0.65,+1.71),
the high energy photon index beta = -2.45(-0.73,+0.30),
the peak energy Ep = 84(-26,+25) keV
(chi2 = 75/49 dof).

The spectrum near the peak count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.54(-0.32,+0.37)
and Ep = 133(-16,+21) keV (chi2 = 44/50 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 42/49 dof).

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


GRB_name: GRB210306A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29642
SUBJECT: Konus-Wind detection of GRB 210306A
DATE:    21/03/10 10:05:25 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia@mail.ioffe.ru>

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

The long-duration GRB 210306A
(Swift-BAT detection: D'Elia et al., GCN 29597, Laha et al., GCN 29617;
Fermi-LAT detection: Ohno et al., GCN 29602;
Fermi-GBM observation: Veres, GCN 29605)
triggered Konus-Wind at T0=14040.731 s UT (03:54:00.731).

The burst light curve shows a multi-peaked emission complex,
which starts at ~T0-0.2 s and has a total duration of ~11 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/GRB210306_T14040/

As observed by Konus-Wind, the burst
had a fluence of 7.01(-0.45,+0.48)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+7.648 s,
of 3.99(-0.60,+0.67)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+16.640 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.21(-0.20,+0.22)
and Ep = 77(-7,+7) keV (chi2 = 48/49 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 46/48 dof).

The spectrum near the peak count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 1 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.17(-0.23,+0.30),
the high energy photon index beta = -2.97(-1.31,+0.34),
the peak energy Ep = 70(-7,+7) keV
(chi2 = 56/49 dof).

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


GRB_name: GRB210308A
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29643
SUBJECT: Konus-Wind detection of GRB 210308A
DATE:    21/03/10 12:11:00 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 210308A
(Swift-BAT detection: D'Elia et al., GCN Circ. 29619,
Palmer et al., GCN Circ. 29633;
Fermi-GBM detection: Lesage et al., GCN Circ. 29626)
triggered Konus-Wind at T0=23879.936 s UT (06:37:59.936).

The burst light curve shows a multi-peaked structure
which starts at ~T0-3.8 s and has a total duration of ~8.9 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/GRB210308_T23879/

As observed by Konus-Wind, the burst
had a fluence of 5.00(-0.48,+0.53)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+1.264 s,
of 3.36(-0.85,+0.87)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 - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.73(-0.32,+0.38)
and Ep = 150(-19,+25) keV (chi2 = 49/55 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 = 49/54 dof).

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


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29644
SUBJECT: GRB 210306A: Tautenburg observations
DATE:    21/03/10 14:33:10 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose@tls-tautenburg.de>

S. Klose, B. Stecklum, A. Nicuesa Guelbenzu, S. Melnikov, and S. Hoegner
(all Tautenburg) report:

We continued observations of the field of GRB 210306A (D'Elia et al., GCN 
29597) with the Tautenburg 1.34m Schmidt telescope. For the optical 
afterglow (Simpson & D'Elia, GCN 29636; Belkin et al., GCN 29635, and 
references therein) we measure:

March 07, 00:21 UT : Rc  = 20.47 +/- 0.13  (Vega mag)

March 07, 02:12 UT : Rc  = 20.53 +/- 0.14

March 07, 19:34 UT : Rc  > 21.2.


Data calibration followed Stecklum et al. (GCN 29604).


GRB_name: GRB210306A
Detection_method: Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29645
SUBJECT: GRB 210306A: LBT observations
DATE:    21/03/11 12:21:33 GMT
FROM:    Andrea Rossi at INAF  <andrea.rossi@inaf.it>

A Rossi (INAF-OAS) 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 2021-03-11, 5.06 
days after the burst trigger. Observations were performed under good 
weather conditions with an average seeing of ~1.2".

We clearly detect the afterglow and we preliminary measure

r=24.2+-0.2 (AB system),

calibrated against SDSS field stars. This is still in agreement with the 
late decay index alpha~1.1 (after an initial plateau ending at ~2hours 
after the burst trigger) obtained modelling the photometry available 
(Strausbaugh et al., GCN29600; Zhu et al., GCN 29607; Hentunen & 
Nissinen GCN 29603; Hosokawa et al., GCN29608; Dimple et al., GCN 29618; 
Belkin et al., GCN 29616, GCN 29620, 29635; Klose et al., GCN 29644).

We acknowledge the excellent support from the LBTO and LBT-INAF staff, 
particularly J. Power, J. Williams F. Cusano, and D. Paris, in obtaining 
these observations.


GRB_name: GRB210312A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29646
SUBJECT: GRB 210312A: Fermi GBM Final Real-time Localization
DATE:    21/03/12 04:14:35 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 04:04:04 UT on 12 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210312A (trigger 637214649.894644 / 210312169).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 68.2, Dec = -16.3 (J2000 degrees, equivalent to J2000 04h 32m, -16d 18'), with a statistical uncertainty of 9.9 degrees.

The angle from the Fermi LAT boresight is 47.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210312169/quicklook/glg_skymap_all_bn210312169.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/bn210312169/quicklook/glg_healpix_all_bn210312169.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210312169/quicklook/glg_lc_medres34_bn210312169.gif


GRB_name: GRB210312A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29648
SUBJECT: Fermi GRB 210312A: Global MASTER-Net observations report 
DATE:    21/03/12 19:30:55 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) started inspect of the Fermi GRB 210312A ( Fermi GBM team, GCN 29646) errorbox  49542 sec after notice time and 49580 sec after trigger time at 2021-03-12 17:50:25 UT, with upper limit up to  20.1 mag. Observations started at twilight.  The observations began at zenith distance = 33 deg. The sun  altitude  is -11.4 deg. 

MASTER-Kislovodsk robotic telescope  located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 210312A errorbox  52229 sec after notice time and 52267 sec after trigger time at 2021-03-12 18:35:12 UT, with upper limit up to  18.3 mag. The observations began at zenith distance = 71 deg. The sun  altitude  is -35.8 deg. 

The galactic latitude b = -37 deg., longitude l = 213 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1566766

We obtain a following upper limits.  

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

   49610 | 2021-03-12 17:50:25 |         MASTER-SAAO | (04h 22m 26.21s , -17d 08m 14.9s) |   C |    60 | 18.7 |        
   49770 | 2021-03-12 17:53:04 |         MASTER-SAAO | (04h 25m 15.76s , -19d 08m 04.1s) |   C |    60 | 18.8 |        
   49849 | 2021-03-12 17:54:24 |         MASTER-SAAO | (04h 39m 05.34s , -17d 07m 13.4s) |   C |    60 | 19.0 |        
   49929 | 2021-03-12 17:55:44 |         MASTER-SAAO | (04h 36m 36.02s , -15d 07m 09.6s) |   C |    60 | 19.2 |        
   50089 | 2021-03-12 17:58:23 |         MASTER-SAAO | (04h 19m 59.21s , -15d 06m 06.2s) |   C |    60 | 19.0 |        
   50168 | 2021-03-12 17:59:43 |         MASTER-SAAO | (04h 42m 08.63s , -19d 06m 29.9s) |   C |    60 | 19.4 |        
   50254 | 2021-03-12 18:01:09 |         MASTER-SAAO | (04h 28m 23.74s , -21d 05m 55.2s) |   C |    60 | 19.4 |        
   50334 | 2021-03-12 18:02:28 |         MASTER-SAAO | (04h 34m 14.90s , -13d 07m 55.1s) |   C |    60 | 19.2 |        
   50414 | 2021-03-12 18:03:48 |         MASTER-SAAO | (04h 17m 52.38s , -13d 06m 08.9s) |   C |    60 | 19.2 |        
   50493 | 2021-03-12 18:05:08 |         MASTER-SAAO | (04h 08m 24.35s , -19d 06m 02.3s) |   C |    60 | 19.4 |        
   50573 | 2021-03-12 18:06:27 |         MASTER-SAAO | (04h 22m 20.34s , -17d 06m 41.6s) |   C |    60 | 19.3 |        
   50653 | 2021-03-12 18:07:47 |         MASTER-SAAO | (04h 30m 41.15s , -17d 05m 41.5s) |   C |    60 | 19.4 |        
   50733 | 2021-03-12 18:09:07 |         MASTER-SAAO | (04h 25m 15.70s , -19d 06m 37.1s) |   C |    60 | 19.5 |        
   50812 | 2021-03-12 18:10:27 |         MASTER-SAAO | (04h 33m 36.32s , -19d 07m 37.3s) |   C |    60 | 19.5 |        
   50892 | 2021-03-12 18:11:47 |         MASTER-SAAO | (04h 45m 28.99s , -21d 05m 47.0s) |   C |    60 | 19.6 |        
   50972 | 2021-03-12 18:13:06 |         MASTER-SAAO | (04h 05m 43.83s , -17d 05m 49.0s) |   C |    60 | 19.4 |        
   51052 | 2021-03-12 18:14:26 |         MASTER-SAAO | (04h 11m 17.39s , -21d 05m 19.2s) |   C |    60 | 19.4 |        
   51131 | 2021-03-12 18:15:46 |         MASTER-SAAO | (04h 31m 58.67s , -23d 07m 24.2s) |   C |    60 | 19.7 |        
   51371 | 2021-03-12 18:19:45 |         MASTER-SAAO | (04h 39m 03.41s , -17d 07m 17.2s) |   C |    60 | 19.6 |        
   51451 | 2021-03-12 18:21:05 |         MASTER-SAAO | (04h 47m 27.90s , -17d 05m 38.3s) |   C |    60 | 19.6 |        
   51530 | 2021-03-12 18:22:25 |         MASTER-SAAO | (04h 36m 23.44s , -15d 06m 11.5s) |   C |    60 | 19.6 |        
   51610 | 2021-03-12 18:23:45 |         MASTER-SAAO | (04h 44m 40.21s , -15d 05m 10.5s) |   C |    60 | 19.5 |        
   51690 | 2021-03-12 18:25:04 |         MASTER-SAAO | (04h 19m 55.83s , -15d 05m 56.8s) |   C |    60 | 19.5 |        
   51783 | 2021-03-12 18:26:38 |         MASTER-SAAO | (04h 28m 05.21s , -15d 06m 57.2s) |   C |    60 | 19.6 |        
   51863 | 2021-03-12 18:27:57 |         MASTER-SAAO | (04h 42m 03.68s , -19d 06m 45.4s) |   C |    60 | 19.8 |        
   51942 | 2021-03-12 18:29:17 |         MASTER-SAAO | (04h 50m 27.68s , -19d 05m 28.1s) |   C |    60 | 20.1 |        
   52022 | 2021-03-12 18:30:37 |         MASTER-SAAO | (04h 28m 21.20s , -21d 06m 44.3s) |   C |    60 | 19.6 |        
   52102 | 2021-03-12 18:31:56 |         MASTER-SAAO | (04h 36m 55.61s , -21d 05m 02.1s) |   C |    60 | 19.6 |        
   52181 | 2021-03-12 18:33:16 |         MASTER-SAAO | (04h 34m 07.95s , -13d 05m 44.7s) |   C |    60 | 19.4 |        
   52261 | 2021-03-12 18:34:36 |         MASTER-SAAO | (04h 42m 19.44s , -13d 04m 45.1s) |   C |    60 | 19.0 |        
   52297 | 2021-03-12 18:35:12 |   MASTER-Kislovodsk | (05h 07m 39.65s , -08d 00m 12.7s) |   C |    60 | 17.5 |        
   52297 | 2021-03-12 18:35:12 |   MASTER-Kislovodsk | (05h 03m 51.59s , -07d 36m 33.1s) |   C |    60 | 18.3 |        
   53353 | 2021-03-12 18:52:47 |   MASTER-Kislovodsk | (05h 07m 38.52s , -08d 00m 53.3s) |   C |    60 | 15.2 |        
   53353 | 2021-03-12 18:52:47 |   MASTER-Kislovodsk | (05h 03m 51.06s , -07d 37m 50.0s) |   C |    60 | 15.7 |        
   54362 | 2021-03-12 19:09:36 |   MASTER-Kislovodsk | (05h 07m 38.90s , -08d 02m 01.0s) |   C |    60 | 15.9 |        
   54362 | 2021-03-12 19:09:36 |   MASTER-Kislovodsk | (05h 03m 53.22s , -07d 38m 45.8s) |   C |    60 | 16.6 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210312B
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29650
SUBJECT: GRB 210312B: A long GRB detected by INTEGRAL
DATE:    21/03/12 22:02:02 GMT
FROM:    Sandro Mereghetti at IASF-Milano/INAF  <sandro.mereghetti@inaf.it>

S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay),  C.Ferrigno,
E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC,
Versoix) and J.Borkowski (CAMK, Torun) report:

a gamma ray burst lasting about 5 s has been detected by IBAS in the
IBIS/ISGRI data at 20:52:17  UT of March 12, 2021

The refined coordinates (J2000) are:
R.A.=  155.8431 deg
DEC.=  +76.8714 deg
with an uncertainty of 2 arcmin (90% c.l.).

The burst had a peak flux of about 1.5 ph/cm2/s (20-200 keV, 1-s
integration time) and a fluence in the same energy range of about 2e-7
erg/cm2

A plot of the light curve will  be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html


GRB_name: GRB210312B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29651
SUBJECT: GRB210312B (Integral alert 9073): Candidate optical afterglow by Ondrejov D50
DATE:    21/03/12 22:05:41 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

M. Jelinek, J. Strobl, S. Trcka, R. Hudec, C. Polasek (ASU CAS Ondrejov)
report:

We observed the position of the Integral trigger 9073 (GRB 210312.87 or B)
with the D50 robotic telescope of the Astronomical Institute Ondrejov, near
Prague, Czech Republic. We performed a series of 10s and 20s unfiltered
exposures starting 23.8 s after the trigger.

In the first images we detect a rapidly fading object not present in the
DSS catalogue at 10:23:15.312 +76:52:06.96 J2000.  The preliminary
magnitude of the
object in the earliest images was R~18m.


GRB_name: GRB210312B
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29652
SUBJECT: GRB 210312B: MASTER OT confirmation
DATE:    21/03/12 22:55:02 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov@xray.sai.msu.ru>

V. Lipunov, V.Kornilov, E.Gorbovskoy,N.Tiurina,P.Balanutsa,F.Balakin,  V.Vladimirov, A.Kuznetsov,K.Zhirkov,D. Vlasenko, I.Gorbunov, D.Zimnukhov, 
V.Senik, A.Chasovnikov,A.Pozdnyakov,V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department),
D. Buckley (South African Astronomical Observatory),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
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)
automatically started (Lipunov et al. GCN 29649)
Integral  GRB 210312B (Mereghetti et al. GCN 29650,Ttrigger=20:52:17UT)
optical observations at MASTER-Kislovodsk at 2021-03-12 20:52:58 UT 
27s after notice time(41s after trigger time),
and 
at MASTER-Tunka at 2021-03-12 20:52:58UT with mli18.7 at first 10s images.
We confirm Jelinek et al. GCN 29651 (Ondrejov) optical counterpart with 
unfiltered m_OT=18.2 at first image.

This message may be cited.


GRB_name: GRB210312B
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29653
SUBJECT: GRB 210312B: GTC photometry
DATE:    21/03/13 00:51:28 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), and R. Scarpa (GTC) report:

We observed the afterglow (Jelinek et al., GCN #29651; Lipunov et al., 
GCN #29652) of INTEGRAL GRB 210312B (Mereghetti et al., GCN #29650) with 
OSIRIS at the 10.4m Gran Telescopio Canarias (Roque de los Muchachos 
Observatory, La Palma, Canary Islands, Spain), starting at 2021-03-12 
22:57:10.834 UT. We obtained a 60 s finding chart exposure under adverse 
conditions (2" seeing, bad transparency because of Calima).

In the image, the afterglow is clearly detected. Against a nearby 
PanSTARRS star, we measure r' = 21.52 +/- 0.06 mag at 2.0898 hr after 
the trigger (0.08708 days).


GRB_name: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29654
SUBJECT: GRB 210306A: HCT optical upper limit
DATE:    21/03/13 04:44:34 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar (IITB), A. Dutta (IIA), R. Gupta (ARIES), V. Bhalerao (IITB), G.
C. Anupama (IIA), S. Barway (IIA), D.K. Sahu (IIA),  A. Kumar (ARIES),
Dimple (ARIES), A. Ghosh (ARIES), S. B. Pandey (ARIES), and K. Misra
(ARIES) report:

We observed GRB 210306A detected by Swift Burst Alert Telescope (V. D'Elia
et. al., GCN 29597) and optical afterglow confirmed by Alan M. Watson et.
al., (GCN 29598) with the 2.0m Himalayan Chandra Telescope (HCT) of the
Indian Astronomical Observatory. We obtained 6 exposures of 300 sec each in
the Bessell R filter. We did not detect the afterglow in our stacked image.
The photometric upper limit is:

--------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Filter | Lim_mag (5-sigma) |

--------------------------------------------------------

2459282.110905 | 58.76 | Bessell R | > 23.22 |

--------------------------------------------------------

The magnitudes are in the AB system of magnitude calibrated against PanSTARRS
(Flewelling et al., 2018) using Lupton's transformation equations available
at http://classic.sdss.org/dr4/algorithms/sdssUBVRITransform.html#Lupton2005.
The magnitudes are not corrected for galactic extinction.

These observations were carried out under the ToO program HCT-2021-C1-P2.
We thank the HCT staff for their support during the observations. The
Indian Astronomical Observatory is operated by the Indian Institute of
Astrophysics, Bengaluru, India.


GRB_name: GRB210312B
Detection_method: INTEGRAL
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29655
SUBJECT: GRB 210312B: Redshift from OSIRIS/GTC
DATE:    21/03/13 13:13:31 GMT
FROM:    Alexander Kann at IAA-CSIC  <kann@iaa.es>

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), and R. Scarpa (GTC) report:

We observed the afterglow (Jelinek et al., GCN #29651; Lipunov et al., 
GCN #29652) of INTEGRAL GRB 210312B (Mereghetti et al., GCN #29650) with 
OSIRIS at the 10.4m Gran Telescopio Canarias (Roque de los Muchachos 
Observatory, La Palma, Canary Islands, Spain), starting at 2021-03-12 
22:57:10.834 UT under adverse conditions (2" seeing, bad transparency 
because of Calima). Following the finding chart exposure (Kann et al., 
GCN #29653), we obtained 2 x 900 s spectroscopic exposures with the 
R1000B grism, covering the spectral range from 3700 to 7800 AA, before 
the telescope was shut down due to worsening observing conditions. We 
detect a faint trace in both images. We resumed observations after an 
improvement in weather conditions at 2021-03-13 01:41:40.281 UT, 
obtaining two further finding charts and 4 x 900 s spectra with the same 
grism.

Using the same comparison star as Kann et al., GCN #29653, we find the 
afterglow has faded to r' = 22.36 +/- 0.03 mag (AB) at 4.8316 hrs after 
the GRB trigger.

Combining the first spectral exposure and the latter, for a total 
exposure of 5 x 900 s, a trace is clearly detected redwards of 4300 AA, 
as well as several absorption lines. We identify these as FeII, MgII, 
and MgI, at a mean redshift of z = 1.069. At this redshift, we also 
detect OII in emission, which allows us to identify this as the redshift 
of the GRB.


GRB_name: GRB210226A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29656
SUBJECT: GRB 210226A: GIT optical upper limit
DATE:    21/03/15 11:33:03 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), K. Sharma (IITB), U. Stanzin (IAO), A. Dutta(IIA), V.
Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the
GIT team:

We observed GRB 210226A detected by Swift-BAT (A. P. Beardmore et al., GCN
29568) with 0.7m GROWTH-India Telescope (GIT). We obtained 10 exposures of
300 sec each in the r' filter. We did not detect any new source in our
stacked image within the 1.5 arcsec circle around R.A.= 08h 16m 27.67s,
DEC.=+57d 35' 02.2". The obtained upper limit follows as:

-------------------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |

-------------------------------------------------------------------

2459272.1074 | 9.84 | 3000 (stacked) | r' | > 20.34 |

-------------------------------------------------------------------

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: GRB210306A
Detection_method: Optical
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29657
SUBJECT: GRB 210306A: GIT optical follow-up
DATE:    21/03/15 11:34:37 GMT
FROM:    Harsh Kumar at Indian Inst of Tech,Bombay  <harshkosli13@gmail.com>

H. Kumar(IITB), K. Sharma (IITB), J. Stanzin (IAO), A. Dutta(IIA), V.
Bhalerao(IITB), G. C. Anupama(IIA), S. Barway(IIA) report on behalf of the
GIT team:

We observed GRB 210306A detected by Swift Burst Alert Telescope (V. D'Elia
et. al., GCN 29597) and optical afterglow confirmed by (Alan M. Watson et.
al., GCN 29598), with the 0.7m GROWTH-India Telescope (GIT). We
obtained multiple
exposures in the r' filter. We clearly detected the afterglow in our stacked
image at R.A. = 08:39:49.99, DEC. = +60:12:19.09. The photometric results
follow as:

--------------------------------------------------------

 JD (mid) | T_mid-T0(hrs) | Filter | Magnitude (AB) |

--------------------------------------------------------

2459280.20139 | 12.9 | r' | 20.87 +/0.05 |

--------------------------------------------------------

The magnitude is in agreement with that reported by Z.P. Zhu et al., (GCN
29607), around the same time of our observation. 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: GRB210317A
Detection_method: Fermi GBM final loc
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29659
SUBJECT: GRB 210317A: Fermi GBM Final Real-time Localization
DATE:    21/03/17 09:18:31 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 09:08:29 UT on 17 Mar 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210317A (trigger 637664914.045098 / 210317381).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 154.2, Dec = -64.9 (J2000 degrees, equivalent to J2000 10h 16m, -64d 54'), with a statistical uncertainty of 1.5 degrees.

The angle from the Fermi LAT boresight is 159.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210317381/quicklook/glg_skymap_all_bn210317381.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/bn210317381/quicklook/glg_healpix_all_bn210317381.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210317381/quicklook/glg_lc_medres34_bn210317381.gif


GRB_name: GRB210317A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29660
SUBJECT: GRB 210317A: GECAM detection
DATE:    21/03/17 12:13:59 GMT
FROM:    QiBin Yi at IHEP, HXMT  <yiqb@ihep.ac.cn>

Q. B. Yi, Y. Huang, S. L. Xiong, S. Xiao, C. Cai, 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,
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 210317A, at 2021-03-17T09:08:28.550 UTC (denoted as T0),
which was also detected by Fermi/GBM (GCN# 29659).

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 70 s.  

An automatic on-ground localization was calculated using the light curves
and counts spectrum in the BDS alert data. 
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: 153.2 deg Dec: -68.1 deg
Err: 3.1 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 location is consistent with the GBM 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_69671308.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: GRB210317A
Detection_method: Fermi GBM Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29661
SUBJECT: Fermi GRB 210317A: Global MASTER-Net observations report 
DATE:    21/03/17 18:15:09 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-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) started inspect of the Fermi GRB 210317A ( Fermi GBM team, GCN 29659) errorbox  30510 sec after notice time and 30572 sec after trigger time at 2021-03-17 17:38:01 UT, with upper limit up to  18.2 mag. Observations started at twilight.  The observations began at zenith distance = 46 deg. The sun  altitude  is -10.1 deg. 

The galactic latitude b = -7 deg., longitude l = 288 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1570432

We obtain a following upper limits.  

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

   30602 | 2021-03-17 17:38:01 |         MASTER-SAAO | (10h 12m 01.88s , -63d 59m 59.4s) |   C |    60 | 17.3 |        
   30682 | 2021-03-17 17:39:21 |         MASTER-SAAO | (10h 20m 18.77s , -66d 00m 32.2s) |   C |    60 | 17.5 |        
   30842 | 2021-03-17 17:42:00 |         MASTER-SAAO | (10h 05m 27.61s , -62d 00m 11.5s) |   C |    60 | 17.5 |        
   31081 | 2021-03-17 17:45:59 |         MASTER-SAAO | (10h 30m 43.04s , -68d 00m 41.0s) |   C |    60 | 18.2 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210318A
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29662
SUBJECT: GRB 210318A: Swift detection of a burst
DATE:    21/03/18 04:09:40 GMT
FROM:    Caryl Gronwall at PSU/Swift-UVOT  <caryl@swift.psu.edu>

E. Troja (NASA/GSFC/UMCP), C. Gronwall (PSU), J.D. Gropp (PSU),
N. J. Klingler (PSU), H. A. Krimm (NSF), A. Y. Lien (GSFC/UMBC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:

At 03:54:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210318A (trigger=1037339).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 33.930, -37.789 which is 
   RA(J2000) = 02h 15m 43s
   Dec(J2000) = -37d 47' 21"
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 30 sec.  The peak count rate
was ~700 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 03:56:35.2 UT, 123.5 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 33.9263, -37.7772 which
is equivalent to:
   RA(J2000)  = 02h 15m 42.32s
   Dec(J2000) = -37d 46' 38.1"
with an uncertainty of 3.2 arcseconds (radius, 90% containment). This
location is 43 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 1.88
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 126 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 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
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
0.016. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
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: GRB210318B
Detection_method: Swift Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29663
SUBJECT: GRB210318B: Swift detection of a burst
DATE:    21/03/18 16:04:20 GMT
FROM:    Eleonora Troja at NASA/GSFC/UMD  <eleonora@umd.edu>

E. Troja (NASA/GSFC, UMCP), K. L. Page (U. Leicester), A. Lien (GSFC/UMBC),
M. Siegel (PSU), and P. Evans (U. Leicester) report on behalf of the Neil
Gehrels Swift Observatory Team:

At 03:08:33 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210318B (trigger=1037335).  Swift slewed immediately to the
burst.
The BAT on-board calculated location is
RA, Dec 264.227, -35.819 which is
   RA(J2000) = 17h 36m 55s
   Dec(J2000) = -35d 49' 08"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty).  The BAT light curve showed several overlapping
pulses with a duration of about 20 sec.  The peak count rate
was ~22000 counts/sec (15-350 keV), at ~3 sec after the trigger.

We have analysed 1.4 ks of XRT data for GRB 210318B, from 52 s to 1.5
ks after the  BAT trigger. The data comprise 584 s in Windowed Timing
(WT) mode (the first 9 s were taken while Swift was slewing) with the
remainder in Photon Counting (PC) mode. The refined XRT position is RA,
Dec = 264.2328, -35.8220 which is equivalent to:

RA (J2000): 17 36 55.88
Dec(J2000): -35 49 19.2

with an uncertainty of 3.5 arcsec (radius, 90% confidence).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.71 (+0.03, -0.04), followed by a break at T+564 s to
an alpha of 1.23 (+0.18, -0.24).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index  of 1.78 (+/-0.09). The
best-fitting absorption column is  1.43 (+/-0.13) x 10^22 cm^-2, in
excess of the Galactic value of 7.1 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.69 (+0.27, -0.25)
and a best-fitting absorption column of 1.6 (+/-0.4) x 10^22 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 6.5 x 10^-11 (1.1 x 10^-10) erg cm^-2
count^-1.

A summary of the PC-mode spectrum is thus:
Total column:        1.6 (+/-0.4) x 10^22 cm^-2
Galactic foreground: 7.1 x 10^21 cm^-2
Excess significance: 4.0 sigma
Photon index:        1.69 (+0.27, -0.25)

If the light curve continues to decay with a power-law decay index of
1.23, the count rate at T+24 hours will be 0.011 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.9 x
10^-13 (1.1 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01037335.

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 57 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 100% of the XRT error circle with a 3-sigma upper limit of 20.1 mag.
No correction has been made for the large, but uncertain, extinction
expected.

Due to a temporary TDRSS outage, no automatic GCN notices or alerts were
promptly distributed.

Burst Advocate for this burst is E. Troja (eleonora@umd.edu).
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: GRB210318B
Detection_method: Konus-Wind Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29664
SUBJECT: Konus-Wind detection of GRB 210318B
DATE:    21/03/18 17:27:52 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 210318B
(Swift-BAT detection: Troja et al., GCN Circ. 29663)
triggered Konus-Wind at T0=11309.57 s UT (03:08:29.570).

The burst light curve shows a multipeaked structure
which starts at ~T0-0.5 s and has a total duration of ~14 s.
The emission is seen up to ~3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210318_T11309/

As observed by Konus-Wind, the burst
had a fluence of 3.83(-0.44,+0.50)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.872 s,
of 1.57(-0.28,+0.29)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+13.824 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.81(-0.12,+0.15),
the high energy photon index beta = -2.51(-0.39,+0.23),
the peak energy Ep = 264(-32,+33) keV
(chi2 = 70/82 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+5.632 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.64(-0.13,+0.14),
the high energy photon index beta = -2.59(-0.45,+0.23),
the peak energy Ep = 297(-32,+36) keV
(chi2 = 67/81 dof).

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


GRB_name: GRB210318A
Detection_method: Swift Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29665
SUBJECT: Swift GRB 210318A: Global MASTER-Net observations report 
DATE:    21/03/18 18:04:28 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 210318A ( E. Troja et al., GCN 29662) errorbox  50452 sec after notice time and 50501 sec after trigger time at 2021-03-18 17:56:12 UT, with upper limit up to  19.7 mag. Observations started at twilight.  The observations began at zenith distance = 58 deg. The sun  altitude  is -14.2 deg. 

The galactic latitude b = -69 deg., longitude l = 248 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=1570922

We obtain a following upper limits.  

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

   50591 |         MASTER-SAAO |   C |   180 | 19.7 |        
Filter C is a clear (unfiltred) band. 


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


GRB_name: GRB210318B
Detection_method: Swift-BAT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29666
SUBJECT: GRB 210318B: Swift-BAT refined analysis
DATE:    21/03/18 20:57:27 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

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

Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210318B (trigger #1037335)
(Troja, et al., GCN Circ. 29663).  The BAT ground-calculated position is
RA, Dec = 264.228, -35.823 deg which is 
  RA(J2000)  =  17h 36m 54.7s 
  Dec(J2000) = -35d 49' 21.4" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 95%.

The mask-weighted light curve shows a multi-peak structure running from ~T-4 sec
to T+15 sec. T90 (15-350 keV) is 14.95 +- 0.50 sec (estimated error including systematics).

The time-averaged spectrum from T-11.22 to T+19.42 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.10 +- 0.13, 
and Epeak of 252.1 +- 191.6 keV (chi squared 41.33 for 0 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.0 +- 0.02 x 10^-5 erg/cm2
and the 1-sec peak flux measured from T+2.70 sec in the 15-150 keV band is
14.5 +- 0.4 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.31 +- 0.03 (chi squared 48.69 for 0 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/1037335/BA/


GRB_name: GRB210318B
Detection_method: Fermi GBM Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29668
SUBJECT: GRB 210318B: Fermi GBM detection
DATE:    21/03/18 21:59:41 GMT
FROM:    Christian Malacaria at NASA-MSFC/USRA  <cmalacaria@usra.edu>

C. Malacaria (NASA-MSFC/USRA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

At 03:08:46.50 UT on 18 March 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210318B (trigger 637729731 / 210318131),
which was also detected by the Swift/BAT (Troja et al. 2019, GCN 29663)
and by Konus-Wind (Svinkin et al. 2021, GCN 29664).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 91 degrees.

The GBM light curve shows a peak
with a duration (T90) of about 24.3 s (50-300 keV).
The time-averaged spectrum from T0-4.1 s to T0+0.0 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is 2.72 +/- 1.53 and
the cutoff energy, parameterized as Epeak, is 84.5 +/- 8.7 keV.

The event fluence (10-1000 keV) in this time interval is
(2.537 +/- 0.393)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-1.9 s in the 10-1000 keV band
is 1.4 +/- 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: GRB210318A
Detection_method: Swift-XRT Det
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29670
SUBJECT: GRB 210318A: Enhanced Swift-XRT position
DATE:    21/03/19 01:16:18 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 1075 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 210318A, 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 = 33.92621, -37.77693 which is equivalent
to:

RA (J2000): 02h 15m 42.29s
Dec (J2000): -37d 46' 36.9"

with an uncertainty of 2.4 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: GRB210318A
Detection_method: Swift-XRT Other
Circular_text:
TITLE:   GCN CIRCULAR
NUMBER:  29671
SUBJECT: GRB 210318A: Swift-XRT refined Analysis
DATE:    21/03/19 04:20:47 GMT
FROM:    Phil Evans at U of Leicester  <pae9@leicester.ac.uk>

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

We have analysed 3.1 ks of XRT data for GRB 210318A (Troja et al. GCN
Circ. 29662), from 107 s to 45.6 ks after the  BAT trigger. The data
comprise 9 s in Windowed Timing (WT) mode (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.
29670).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.09 (+0.27, -0.29).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+0.6, -0.5). The
best-fitting absorption column is  1.4 (+1.9, -1.2) x 10^21 cm^-2,
consistent with the Galactic value of 1.9 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 3.8 x 10^-11 (4.6 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:      1.4 (+1.9, -1.2) x 10^21 cm^-2
Galactic foreground: 1.9 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:      1.8 (+0.6, -0.5)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01037339.

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


