| Summary table |
|---|
| Variable |
Value |
Source |
| T0 |
10:34:09.519 UTC |
GCN_circulars,Konus-Wind Det |
| ra |
221.0242° |
Swift |
| decl |
-25.6349° |
Swift |
| pos_error |
2.07e-04° |
Swift |
| T90 |
1.15 s |
Swift |
| T90_start |
10:34:12 UTC |
Swift |
| fluence |
3.80e-07 erg/cm² |
Swift |
| T100 |
3.631 s |
|
| GBM_located |
False |
|
| mjd |
57265.44038795139 |
GCN_circulars,Konus-Wind Det |
| IPN table |
|---|
| GRB_name |
GRB150831A |
| ra |
221.0208° |
| decl |
-25.6500° |
| pos_error |
5.00e-02° |
| Swift table |
|---|
| GRB_name |
GRB150831A |
| t_trigger |
10:34:12 UTC |
| ra |
221.0242° |
| decl |
-25.6349° |
| pos_error |
2.07e-04° |
| T90 |
1.15 s |
| fluence |
3.80e-07 erg/cm² |
| GCN 18209 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18209 |
| Detection_method |
Swift Det |
| t_trigger |
10:34:12 UTC |
| ra |
221.0230° |
| decl |
-25.6490° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18209
SUBJECT: GRB 150831A: Swift detection of a short burst
DATE: 15/08/31 10:51:14 GMT
FROM: Jamie A. Kennea at PSU/Swift-XRT
A. Y. Lien (GSFC/UMBC), D. N. Burrows (PSU) and J. A. Kennea (PSU)
report on behalf of the Swift Team:
At 10:34:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150831A (trigger=653838). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 221.023, -25.649 which is
RA(J2000) = 14h 44m 05s
Dec(J2000) = -25d 38' 57"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a short pulse
with a duration of about 1.2 sec. The peak count rate
was ~10000 counts/sec (15-350 keV), at ~ 0.1 sec after the trigger.
The XRT began observing the field at 10:35:36.3 UT, 83.4 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 221.0245,
-25.6356 which is equivalent to:
RA(J2000) = 14h 44m 05.87s
Dec(J2000) = -25d 38' 08.2"
with an uncertainty of 2.6 arcseconds (radius, 90% containment). This
location is 48 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.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.14
x 10^21 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 8.91e-10 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 88 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
0.11.
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/too.html.)
|
| GCN 18210 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18210 |
| Detection_method |
INTEGRAL |
| t_trigger |
10:34:24 UTC |
| ra |
221.0207° |
| decl |
-25.6474° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18210
SUBJECT: INTEGRAL detection of GRB 150831A
DATE: 15/08/31 11:41:33 GMT
FROM: Sandro Mereghetti at IASF/CNR
S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo,
L.Ducci (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the
IBAS Localization Team report:
GRB 150831A (Lien et al. GCN 18209) has been detected by IBAS in the
IBIS/ISGRI data with a significance slightly below the threshold for
automatic alert delivery (IBAS Weak Alert n.7228 was distributed at
10:34:24 UT).
The burst consists of a single peak with duration of 2 s and starting at
10:34:12 UT.
The IBIS/ISGRI refined coordinates (J2000) are:
R.A.= 221.0207 deg
DEC.= -25.6474 deg
with an uncertainty of 3 arcmin (90% c.l.).
The burst had a fluence of about 3x10e-7 erg/cm2 in the the 20-200 keV
energy range.
A plot of the light curve will be posted at
http://ibas.iasf-milano.inaf.it/IBAS_Results.html
|
| GCN 18211 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18211 |
| Detection_method |
Optical |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18211
SUBJECT: GRB 150831A: optical upper limit ISON-SSO
DATE: 15/08/31 13:02:17 GMT
FROM: Alexei Pozanenko at IKI, Moscow
L. Elenin (KIAM), A. Volnova (IKI), E. Mazaeva (IKI), I. Molotov (KIAM),
A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of Swift and INTEGRAL short GRB 150309A (Lien et
al., GCN 18209; Mereghetti et al., GCN 18210) with with 0.4-m f/2.4
telescope of ISON-SSO (Siding Spring Observatory) starting on Aug. 31
(UT) 10:44:10 (i.e. 10 minutes after burst trigger). We obtained 30
unfiltered images of 30 s exposure. We do not detect any optical source
within XRT error circle (Lien et al., GCN 18209). Preliminary photometry
of the filed is following
Date UT start t-T0 Filter Exp. UL (3 sigma)
(mid, days) (s)
2015-08-31 10:44:10 0.01299 none 30*30 18.8
Photometry is based on nearby USNO-B1.0 stars (R2)
|
| GCN 18212 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18212 |
| Detection_method |
Swift-XRT Det |
| ra |
221.0242° |
| decl |
-25.6350° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18212
SUBJECT: GRB 150831A: Enhanced Swift-XRT position
DATE: 15/08/31 16:33:51 GMT
FROM: Phil Evans at U of Leicester
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1089 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 150831A, 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 = 221.02422, -25.63499 which is equivalent
to:
RA (J2000): 14h 44m 5.81s
Dec (J2000): -25d 38' 06.0"
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.
|
| GCN 18214 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18214 |
| Detection_method |
Swift-BAT Det |
| ra |
221.0340° |
| decl |
-25.6190° |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18214
SUBJECT: GRB 150831A: Swift-BAT refined analysis
DATE: 15/08/31 19:08:41 GMT
FROM: Amy Lien at GSFC
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), J. Norris (BSU), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), (i.e. the Swift-BAT team):
Using the data set from T-240 to T+938 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150831A (trigger #653838)
(Lien, et al., GCN Circ. 18209). The BAT ground-calculated position is
RA, Dec = 221.034, -25.619 deg which is
RA(J2000) = 14h 44m 08.1s
Dec(J2000) = -25d 37' 08.4"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 52%.
The mask-weighted light curve shows a short pulse that starts and peaks
at ~ T0, and ends at ~ T+1.4 s. T90 (15-350 keV) is 1.15 +- 0.23 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.03 to T+1.40 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
0.81 +- 0.16. The fluence in the 15-150 keV band is 3.8 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.0 sec in the 15-150 keV band
is 3.4 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The lag analysis using 8-ms binned light curve gives a spectral lag
of -2 ms +- 5 ms for the 100-350 keV and 25-50 keV band,
and 13 ms +- 20 ms for the 50-100 keV and 15-25 keV band.
These values are consistent with short GRBs.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/653838/BA/
|
| GCN 18216 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18216 |
| Detection_method |
Swift-XRT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18216
SUBJECT: GRB 150831A: Swift-XRT refined Analysis
DATE: 15/08/31 22:51:03 GMT
FROM: Phil Evans at U of Leicester
A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU),
T.G.R. Roegiers (PSU), L.M. McCauley (PSU), K.L. Page (U. Leicester),
C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia
(ASDC) and A.Y. Lien report on behalf of the Swift-XRT team:
We have analysed 8.6 ks of XRT data for GRB 150831A (Lien et al. GCN
Circ. 18209), from 72 s to 22.5 ks after the BAT trigger. The data
comprise 8 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.
18212).
The light curve can be modelled with a power-law decay with a decay
index of alpha=2.52 (+0.21, -0.22).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.25 (+0.17, -0.12). The
best-fitting absorption column is 1.27 (+0.89, -0.13) 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 5.0 x 10^-11 (5.4 x
10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
Total column: 1.27 (+0.89, -0.13) x 10^21 cm^-2
Galactic foreground: 1.1 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.25 (+0.17, -0.12)
If the light curve continues to decay with a power-law decay index of
2.52, the count rate at T+24 hours will be 2.1 x 10^-7 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x
10^-17 (1.2 x 10^-17) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00653838.
This circular is an official product of the Swift-XRT team.
|
| GCN 18218 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18218 |
| Detection_method |
Swift-UVOT Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18218
SUBJECT: GRB 150831A: Swift/UVOT Upper Limits
DATE: 15/09/01 00:14:09 GMT
FROM: Mike Siegel at PSU/Swift MOC
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 150831A
88 s after the BAT trigger (Lien et al., GCN Circ. 18209).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 18212)
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 88 238 147 >20.5
u_FC 300 550 246 >19.9
white 88 6622 746 >21.2
v 631 17885 1356 >19.8
b 557 6417 452 >20.4
u 300 12784 1326 >21.0
w1 680 12112 1153 >21.3
m2 655 18529 1750 >21.3
w2 607 16972 1357 >21.1
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.11 in the direction of the burst
(Schlegel et al. 1998).
|
| GCN 18219 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18219 |
| Detection_method |
GROND |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18219
SUBJECT: GRB 150831A: GROND Upper Limits
DATE: 15/09/01 03:00:06 GMT
FROM: Fabian Knust at MPE/GROND
F. Knust (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 150831A (Swift trigger 653838; Lien et al., GCN #18209) simultaneously in g'r'i'z'JHK
with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).
Observations started at 23:21UT on 2015-08-31, 13hrs after the GRB trigger. They were performed at
an average seeing of 2.4" and at an average airmass of 1.5.
We do not detect a source within the Swift-XRT error circle reported by Osborne et al. (GCN #18212) down to
g'> 24.9 mag,
r'> 24.5 mag,
i'> 23.8 mag,
z'> 23.8 mag,
J> 21.4 mag,
H> 20.9 mag, and
K> 18.6 mag.
The given limits are derived based on calibrating the images against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.1 mag in the direction of the burst (Schlegel et al. 1998). |
| GCN 18226 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18226 |
| Detection_method |
Konus-Wind Det |
| t_trigger |
10:34:09.519 UTC |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18226
SUBJECT: Konus-Wind observation of GRB 150831A
DATE: 15/09/01 15:51:15 GMT
FROM: Dmitry Svinkin at Ioffe Institute
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:
The short-duration GRB 150831A (Swift trigger 648437:
Lien, et al., GCN Circ. 18209; Ukwatta, et al., GCN Circ. 18214;
INTEGRAL detection: Mereghetti et al., GCN Circ. 18210)
triggered Konus-Wind at T0=38049.519 s UT (10:34:09.519).
The burst light curve shows a short pulse with
a total duration of ~1 s.
As observed by Konus-Wind, the burst had a fluence of
(2.4 +/- 0.4)x10^-6 erg/cm2, and a 16-ms peak flux,
measured from T0-0.082 s, of (9.1 +/- 2.5)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
Since the most intense part of the burst was detected before
the trigger, the spectral analysis was performed using
the KW 3-channel light curve data.
Modeling the 3-channel time-integrated spectrum
(from T0-0.108 s to T0+0.912 s) by a power law
with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.5 +/- 0.3, and Ep = 564 +/- 122 keV.
The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB150831_T38049/
All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.
|
| GCN 18235 table |
|---|
| GRB_name |
GRB150831A |
| GCN_number |
18235 |
| Detection_method |
Other |
| Circular_text |
TITLE: GCN CIRCULAR
NUMBER: 18235
SUBJECT: GRB 150831A: 9.8 GHz VLA upper limits
DATE: 15/09/04 00:16:23 GMT
FROM: Wen-fai Fong at U of Arizona
W. Fong (U. Arizona) and B. A. Zauderer (Harvard) report:
"We observed the field of the short-duration GRB 150831A (Lien et al., GCN
18209) with the Karl G. Jansky Very Large Array (VLA) beginning on 2015 Aug
31.934 UT (11.9 hr post-burst) at a mean frequency of 9.8 GHz. In 1 hour of
observations, we do not detect any radio source within or around the
enhanced XRT position (Osborne et al., GCN 18212) to a 3-sigma limit of 25
microJy. Furthermore, we obtained a second set of observations beginning on
2015 Sep 2.954 UT (2.5 days post-burst) at a mean frequency of 9.8 GHz and
do not detect any radio source in or around the XRT position to a 3-sigma
limit of 21 microJy.
We therefore place 3-sigma limits of 25 microJy and 21 microJy on the radio
afterglow of GRB 150831A at 11.9 hr and 2.5 days after the burst,
respectively.
We thank the VLA staff for quickly executing these observations."
|