GRB 120923A
GCN Circular 13825
Subject
GRB 120923A: Correction to GCN 13823
Date
2012-09-28T07:33:43Z (13 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
M. Im (CEOU/SNU) reports
The UT date reported in GCN 13823 should be 2012-09-23,
rather than 2012-09-29.
We thank J. Fynbo for spotting the error.
GCN Circular 13823
Subject
GRB 120923A: JHK Observation
Date
2012-09-28T06:48:44Z (13 years ago)
From
Myungshin Im at Seoul Nat U <mim@astro.snu.ac.kr>
M. Im (CEOU/SNU), H.-I. Sung (KASI), and Y. Urata (NCU)
on behalf of a larger collaboration.
We observed the field of GRB 120923A (Yershov et al. GCN 13796)
in JHK using KASINICS on the 1.8m telescope at the Bohyunsan
observatory in Korea.
The observation started at 2012-09-29 11:30:43 UT,
or about 6.25 hours after the BAT alert.
The stacked JHK images do not reveal a convincing detection
of the afterglow reported earlier (Levan et al. GCN 13802),
to the limits of ~20 AB mag in H and K (3-sigma).
[GCN OPS NOTE(03oct12): See GCN Circ 13825 for a correction.]
GCN Circular 13820
Subject
GRB 120923A: optical upper limit
Date
2012-09-26T20:24:47Z (13 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
L. Elenin (KIAM), A. Volnova (SAI MSU, IKI), I. Molotov (KIAM), A. Pozanenko
(IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 120923A (Yershov et al., GCN 13796)
with 0.45-m telescope of ISON-NM observatory starting on Sep. 23 (UT)
05:18:58, i.e 172 s after burst trigger. We took several unfiltered images
of 30 s and 60 s exposures. We do not detect the optical counterpart (Levan
et al., GCN 13802). A photometry of co-added frames is based on the
USNO-B1.0 (R2) nearby stars is following:
T0+, Exposure, OT, UL (3 sigma)
mid, d (s)
0.00447 9x30 n/d 19.7
0.02839 53x30 n/d 20.5
GCN Circular 13818
Subject
GRB 120923A: RAPTOR Early Afterglow Limits
Date
2012-09-25T23:45:36Z (13 years ago)
From
James Wren at LANL <jwren@nis.lanl.gov>
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:
The RAPTOR network of robotic optical telescopes made follow-up observations
of Swift trigger 534402 (Yershov, et al., GCN 13796). Our narrow-field
instruments in Los Alamos, NM, began imaging at 05:17:43.06 UT, 96.8 s after
the Swift BAT trigger. We do not detect the optical counterpart (Levan,
et al., GCN 13802) in any of our images. The following table summarizes some
of our early observations. Our unfiltered images are calibrated to the
USNO-B1 r-band. The start time is seconds since the BAT trigger time. The
magnitude limit is the 3-sigma detection threshold.
T-Start Exp-Time Mag-Limit
----------------------------------
96.82 5.9 17.3
106.83 5.4 17.6
143.24 5.4 17.5
161.53 5.1 17.5
181.82 10.1 18.2
220.22 10.4 18.1
284.22 10.9 18.1
GCN Circular 13817
Subject
GRB 120923A: MITSuME Okayama Optical upper limits
Date
2012-09-25T05:54:47Z (13 years ago)
From
Daisuke Kuroda at OAO/NAOJ <dikuroda@oao.nao.ac.jp>
D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 120923A (Yershov et al., GCNC 13796)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2012-09-23 10:00:39 UT (~4.7 h after the burst)
We did not find any new point source within the enhanced XRT circle
(Goad et al., GCNC 13801) in all the three bands.
We also could not detect the previously reported afterglow (Levan et al.,
GCNC 13802).
Three sigma upper limits of the OT are listed below. We used
SDSS catalog for flux calibration.
T0+[day] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------
0.23958 11:01:05 6360.0 >20.6 >20.2 >18.9
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
GCN Circular 13815
Subject
GRB 120923A: RAPTOR Limits During Gamma-Ray Emitting Interval
Date
2012-09-24T22:42:24Z (13 years ago)
From
James Wren at LANL <jwren@nis.lanl.gov>
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:
The RAPTOR network of robotic optical telescopes made observations of Swift
trigger 534402 (Yershov, et al., GCN 13796). The burst location was within
the field of our wide-field monitor located in Maui, HI, which began a 10 s
integration of the location at 05:16:05.26 UT, 1.0 s before the Swift trigger
time and during the gamma-ray emitting interval. The next 10 s exposure began
at 05:16:23.26, 17.0 s after the Swift trigger and covering the peak emission
detected by the BAT (Markwardt, et al., GCN 13807). The optical counterpart
(Levan, et al., GCN 13802) was not detected above our 3-sigma limiting
magnitude of 10.5 based on a comparison of our unfiltered image to the
Tycho-2 V-band catalog.
GCN Circular 13814
Subject
GRB 120923A: CARMA Observations
Date
2012-09-24T16:24:29Z (13 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
A. Zauderer and E. Berger (Harvard) report on behalf of the CARMA Key
Project "A Millimeter View of the Transient Universe":
"We observed the position of GRB 120923A (Yershov et al; GCN 13796) with
the Combined Array for Research in Millimeter Astronomy (CARMA)
beginning on 2012 Sep 23.99 UT (0.77 d after the burst). Observations
were obtained at a mean frequency of ~85 GHz. We find no significant
millimeter emission at the position of the near-IR counterpart (Levan et
al; GCN 13802) or within the enhanced Swift/XRT error circle (Goad et
al; GCN 13801) to a preliminary 3-sigma limit of 0.39 mJy."
GCN Circular 13813
Subject
GRB 120923A: EVLA Observations
Date
2012-09-24T16:23:18Z (13 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
A. Zauderer, E. Berger, and T. Laskar (Harvard) report on behalf of a
larger collaboration:
"We observed the position of GRB 120923A (Yershov et al; GCN 13796)
beginning on 2012 Sep 24.02 UT (0.8 d after the burst) with the EVLA at
a mean frequency of 5.8 GHz. We find no significant radio emission at
the position of the near-IR counterpart (Levan et al; GCN 13802) or
within the enhanced Swift/XRT error circle (Goad et al; GCN 13801) to a
3-sigma limit of 28 uJy."
GCN Circular 13812
Subject
GRB 120923A: Swift-XRT refined Analysis
Date
2012-09-24T05:28:05Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P. Beardmore
(U. Leicester), P.A. Evans (U. Leicester), O.M. Littlejohns (U.
Leicester), B. Sbarufatti (INAF-OAB/PSU), G. Stratta (ASDC), P.
D'Avanzo (INAF-OAB) and V.N. Yershov report on behalf of the Swift-XRT
team:
We have analysed 9.0 ks of XRT data for GRB 120923A (Yershov et al.
GCN Circ. 13796), from 151 s to 57.5 ks after the BAT trigger. The
data comprise 331 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 13801).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.84 (+0.11, -0.09).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.78 (+0.47, -0.26). The
best-fitting absorption column is 1.08 (+1.30, -0.10) x 10^21 cm^-2,
consistent with the Galactic value of 9.8 x 10^20 cm^-2 (Kalberla et
al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 4.2 x 10^-11 (5.1 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.08 (+1.30, -0.10) x 10^21 cm^-2
Galactic foreground: 9.8 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.78 (+0.47, -0.26)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00534402.
This circular is an official product of the Swift-XRT team.
GCN Circular 13811
Subject
GRB 120923A: GROND Upper limits
Date
2012-09-24T03:01:34Z (13 years ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
F. Knust (MPE Garching), S. Klose, A. Nicuesa Guelbenzu (both TLS
Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND
team:
We observed the field of GRB 120923A (Swift trigger 534402; Yershov et
al., GCN 13796) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).
Observations started at 00:10 UT on Sep 24, 19 hrs after the GRB trigger,
and are continuing. In a first 30 min exposure, at a mid time 00:35 UT, we
do not detect any source at the position of the NIR transient reported by
Levan et al. (GCN 13802) down to (AB mags, 3 sigma)
g' > 23.5,
r' > 23.7,
i' > 23.0,
z' > 23.0,
J > 21.0,
H > 20.4.
These uper limits are derived based on calibrating the images against
GROND zeropoints and 2MASS field stars and are not corrected for the
Galactic foreground extinction corresponding to a reddening of E_(B-V)=
0.15 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular 13807
Subject
GRB 120923A: Swift-BAT refined analysis
Date
2012-09-23T13:37:37Z (13 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU), V. N. Yershov (UCL-MSSL)
(i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120923A (trigger #534402)
(Yershov, et al., GCN Circ. 13796). The BAT ground-calculated position is
RA, Dec = 303.781, 6.255 deg, which is
RA(J2000) = 20h 15m 07.3s
Dec(J2000) = +06d 15' 16.8"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.
The mask-weighted light curve shows the burst starting at ~T-5 sec, peaking
at ~T+25 sec, and ending at ~T+30 sec. T90 (15-350 keV) is 27.2 +- 3.0 sec
(estimated error including systematics).
The time-averaged spectrum from T-2.93 to T+26.64 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index -0.29 +- 1.66,
and Epeak of 44.4 +- 10.6 keV (chi squared 43.83 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 3.2 +- 0.8 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+24.67 sec in the 15-150 keV band is
0.6 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.80 +- 0.23 (chi squared 51.10 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/534402/BA/
GCN Circular 13805
Subject
GRB 120923A: Swift/UVOT Upper Limit
Date
2012-09-23T12:50:40Z (13 years ago)
From
Alice Breeveld at MSSL-UCL <aab@mssl.ucl.ac.uk>
A. A. Breeveld (MSSL-UCL), V. N. Yershov (MSSL-UCL) and N. P. M. Kuin
(MSSL-UCL) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 120923A
143 s after the BAT trigger (Yershov et al., GCN Circ. 13796).
No optical afterglow consistent with the XRT or Gemini position (Goad et
al., GCN Circ. 13801, Levan et al., GCN Circ. 13802) is detected in the
initial UVOT exposure.
A preliminary 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding
chart exposure is:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 143 293 147 >21.3
The magnitude in the table is not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.16 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 13802
Subject
GRB 120923A: Gemini afterglow detection, high-z candidate
Date
2012-09-23T10:33:17Z (13 years ago)
From
Andrew Levan at U.of Leicester <A.J.Levan@warwick.ac.uk>
A.J. Levan (U. Warwick), D.A. Perley (Caltech), N.R. Tanvir (U. Leicester) and A. Cucchiara (UCSC) report for a larger collaboration:
"We observed the location of GRB 120923A (Yershov et al. GCN 13796) with Gemini-North, beginning approximately 1.4 hours after the burst. Observations were obtained in riz (with GMOS) and YJHK (with NIRI). In our optical and Y-band observations we detect no source in the refined XRT error circle (Goad et al. GCN 13801), with a preliminary z-band limit of z~24. However, in our JHK observations we clearly detect a source at a location of
RA(J2000): 20:15:10.78
DEC(J2000): 06:13:16.3
(uncertainty ~0.5")
Which is seen to fade in two epochs of J-band observations separated by ~3 hours, confirming it as the counterpart of GRB 120923A. The colours of this source in the IR are blue, with H-K~0.1 mag. This is strongly suggestive of a break between the Y and J-band, similar to GRB 090423, and may indicate that GRB 120923A lies at z~8.
We thank Michael Hoenig for excellent support for these observations.
Further observations are ongoing."
GCN Circular 13801
Subject
GRB 120923A: Enhanced Swift-XRT position
Date
2012-09-23T07:49:51Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.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 1113 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 120923A, 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 = 303.79480, +6.22131 which is equivalent
to:
RA (J2000): 20h 15m 10.75s
Dec (J2000): +06d 13' 16.7"
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.
GCN Circular 13798
Subject
GRB 120923A: TAROT La Silla observatory optical observations
Date
2012-09-23T06:00:56Z (13 years ago)
From
Alain Klotz at CESR-CNRS <Alain.Klotz@free.fr>
Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:
We imaged the field of GRB 120923A detected by SWIFT
(trigger 534402) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.
The observations started 104.6s after the GRB trigger
(16.8s after the notice). The elevation of the field decreased
from 16 degrees above horizon and weather conditions
were good.
The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT at the XRT position (Yershov et al.
GCNC 13796) with a limiting magnitude of:
t0+105s to t0+165s : R > 16.0
We co-added a series of exposures:
t0+178s to t0+329s : R > 17.9
Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.
Note that there is NOMAD1 0962-0583888 (R.A.=303.7958222
Decl=+06.2200278 J2000) R=17.9 very close to the XRT position.
This source is detected on TAROT images but the sampling of
TAROT (3.3 arcsec/pixel) does not allow to separate an OT
from this star.
This message may be cited.
GCN Circular 13797
Subject
GRB 120923A: ROTSE-III Optical Limits
Date
2012-09-23T05:41:38Z (13 years ago)
From
Weikang Zheng at U.of Michigan <zwk@umich.edu>
W. Zheng (U Mich) and T. Guver (Sabanci U) report on behalf of the ROTSE
collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB 120923A
(Swift trigger 534402; Yershov et al., GCN 13796), producing images
beginning 0.7 s after the GCN notice time. An automated response took the
first image at 05:17:43.7 UT, 97.4 s after the burst, under fair conditions.
We took 10 5-sec, 10 20-sec and 0 60-sec exposures. These unfiltered images
are calibrated relative to USNO A2.0 (R). Imaging is on going.
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma Swift/BAT error circle. Individual images have limiting magnitudes
ranging from 15.4-16.3; we set the following specific limits.
start UT end UT t_exp(s) mlim Coadd?
------------------------------------------------------
05:17:43 05:17:48 5 15.6 N
05:17:55 05:18:00 5 15.4 N
05:18:07 05:18:12 5 15.7 N
05:17:43 05:19:31 50 16.4 Y
GCN Circular 13796
Subject
GRB 120923A: Swift detection of a burst
Date
2012-09-23T05:28:11Z (13 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
V. N. Yershov (UCL-MSSL), S. D. Barthelmy (GSFC),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
C. J. Mountford (U Leicester), S. R. Oates (UCL-MSSL),
K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of
the Swift Team:
At 05:16:06 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120923A (trigger=534402). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 303.795, +6.235 which is
RA(J2000) = 20h 15m 11s
Dec(J2000) = +06d 14' 05"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows several overlapping peaks
with a total duration of about 35 sec. The peak count rate
was ~700 counts/sec (15-350 keV), at ~6 sec after the trigger.
The XRT began observing the field at 05:18:26.0 UT, 139.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 303.79631, 6.22039 which is equivalent
to:
RA(J2000) = 20h 15m 11.11s
Dec(J2000) = +06d 13' 13.4"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This
location is 52 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. 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 9.80
x 10^20 cm^-2 (Kalberla et al. 2005).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 143 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
0.16.
Burst Advocate for this burst is V. N. Yershov (vny AT mssl.ucl.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/too.html.)