GRB 121128A
GCN Circular 14256
Subject
GRB 121128A: optical observations in Mondy observatory
Date
2013-03-04T20:20:57Z (13 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A.Volnova (SAI MSU), E. Klunko (ISTP), A. Pozanenko (IKI) report on
behalf of larger GRB follow-up collaboration:
We report revised results of our observations in Mondy observatory (GCNs
14019, 14024) of the afterglow of GRB 121128A (Oates et al., GCN 14007;
Japelj et al., GCN 14008). We re-processed data obtained on Nov. 28,29
and Dec. 02 based on full data set obtained.
Nov. 28
t_start, filter, exp, T-t0, OT, err
UT s d
10:27:30 R 4*30+16*60 0.23024 19.79 0.05
10:46:51 R 10*60 0.24047 19.85 0.04
10:56:58 R 10*60 0.24751 19.78 0.04
11:07:06 R 10*60 0.25454 19.96 0.05
11:17:14 R 8*60+12*40 0.26674 19.95 0.05
11:42:14 R 25*40 0.28132 20.07 0.05
11:59:13 R 30*40 0.29429 20.12 0.05
12:19:36 R 30*40 0.30845 20.06 0.04
12:39:58 R 30*40 0.32259 20.24 0.05
13:00:21 R 64*40 0.34488 20.32 0.04
Nov. 29
t_start, filter, exp, T-t0, OT, UL(3sigma)
UT s d
10:16:58 R 6220 1.27406 n/d 23.3
Dec. 02
t_start, filter, exp, T-t0, OT, UL(3sigma)
UT s d
10:47:17 R 4920 4.32854 n/d 21.2
The photometry is based on following reference stars
1442-0304687 20:02:23.58 +54:16:58.9 16.67
1442-0304744 20:02:29.58 +54:16:57.0 18.66
1442-0304807 20:02:36.33 +54:17:58.9 18.20
1443-0305750 20:02:37.10 +54:18:34.6 17.72
1443-0305710 20:02:32.72 +54:18:46.9 17.25
The combined light curve of our observations (this circular, GCN 14201
and GCN 14255) can be found at
http://grb.rssi.ru/GRB121128A/GRB121128A_lc2.PNG
Non-filtered photometry of Abastumani observatory (GCN 14201) is
corrected to the R as d(C-R)=-0.034. One can see non-monotonous behavior
of the lc between 0.4 -- 0.4 days after trigger, and probable jet brake
between 0.6 and 1.3 days.
GCN Circular 14255
Subject
GRB 121128A: optical upper limit in Maidanak observatory
Date
2013-03-04T20:09:12Z (13 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), A. Volnova (SAI MSU), A. Sergeev (Institute of Radio
Astronomy of NASU), O. Burhonov (UBAI), I. Molotov (KIAM) report on
behalf of larger GRB follow-up collaboration:
We observed the field of Swift GRB 121128A (Oates et al., GCN 14007)
with AZT-22 telescope of Maidanak observatory starting on Nov. 30 (UT)
13:47:48 under mean seeing (FWHM) of about 1 arcsec. We obtained several
images of 180 s exposure in R filter. The optical afterglow
(Oates et al., GCN 14007; Japelj et al., GCN 14008) is not detected in
our images. A photometry of the stacked image is based on nearby
USNO-B1.0 stars:
t_start, T0+ (mid), filter, exp., OT, Upper Limit(3sigma)
(UT) d s
13:47:48 2.37924 R 15x180 n/d 23.7
GCN Circular 14201
Subject
GRB 121128A: optical observations
Date
2013-02-13T16:37:16Z (13 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
Yu. Krugly (Institute of Astronomy of Kharkiv National University),
R.Inasaridze, O. Kvaratskhelia(Abastumani Astrophysical Observatory),
I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB
follow-up collaboration:
We observed the field of the Swift Swift GRB 121128A (Oates et al., GCN
14007)with AC-32 (0.7m Maksutov) telescope of Abastumani Observatory,
starting on Nov. 28 (UT) 15:28. We took several unfiltered images of 300
s exposure. We detected the afterglow (Oates et al., GCN 14007; Japelj
et al., GCN 14008) in stacked images. The photometry of a the stacked
image is based on USNO-B1.0 stars (R2):
Start, T0+, Filter, Exp., OT
(UT) (mid),days
15:27:50 0.4479 none 9x300 20.24 +/- 0.12
16:18:59 0.4853 none 8x300 20.35 +/- 0.16
17:09:58 0.5208 none 8x300 20.38 +/- 0.18
18:01:17 0.5544 none 9x300 20.55 +/- 0.22
18:46:44 0.5871 none 8x300 20.84 +/- 0.36
GCN Circular 14043
Subject
GRB 121128A: Optical Observations
Date
2012-12-04T05:24:30Z (13 years ago)
From
Shashi Bhushan Pandey at ROTSE <shaship@umich.edu>
S.B. Pandey and Brajesh Kumar (ARIES Nainital, India, on behalf of larger
Indian GRB collaboration)
We observed GRB 121128A (Swift trigger 539866, Oates et al. 2012, GCN
Circ.14007) field with the 1.04m telescope at ARIES, Nainital starting at
2012-11-28 14:02:55 (UT). Several images in R_c and I_c pass-bands were
obtained.
The optical afterglow candidate ( Oates et al. 2012, GCN Circ.14007,
Japelj
et al. 2012, GCN Circ. 14008) was clearly detected in our frames. The
preliminary photometry of the co-added R_c (300sec x 3) and I_c (300sec x
3) frames yield following magnitudes.
--------------------------------------------------------------------------
Time (MID-UT) Exp (sec) Filter Magnitude
--------------------------------------------------------------------------
2012-11-28, 14:12:11 900 R_c 20.35 +/- 0.05
2012-11-28, 14:55:40 900 I_c 19.65 +/- 0.11
--------------------------------------------------------------------------
Nearby USNO stars have been used for calibration.
This massage may be cited.
GCN Circular 14024
Subject
GRB 121128A: optical observation in Mondy observatory
Date
2012-11-30T21:19:10Z (13 years ago)
From
Alina Volnova at SAI MSU <alinusss@gmail.com>
A.Volnova (SAI MSU, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) on behalf of
larger GRB follow up collaboration report:
We observed the field of the Swift GRB 121128A (Oates et al., GCN 14007)
with AZT-33IK telescope of Sayan observatory (Mondy). We took several
images in R-filter of 60 s exposure on Nov. 29, between (UT) 10:16:58-
13:33:38 under favorable weather conditions. We do not detect the optical
afterglow (Oates et al., GCN 14007; Japelj et al., GCN 14008) in stacked
images. A photometry of stacked image
t_start, T0+ (mid), filter, exp., UL (3 sigma)
(UT) d s
10:16:58 1.28450 R 11200 22.1
is based on the same nearby USNO-B1.0 stars used in our previous
observation (Volnova et al., GCN 14019):
USNO-B1.0 RA(J2000) Dec(J2000) R
1442-0304687 20:02:23.58 +54:16:58.9 16.67
1442-0304744 20:02:29.58 +54:16:57.0 18.66
1442-0304807 20:02:36.33 +54:17:58.9 18.20
1443-0305750 20:02:37.10 +54:18:34.6 17.72
1443-0305710 20:02:32.72 +54:18:46.9 17.25
GCN Circular 14023
Subject
GRB 121128A: MITSuME Akeno Optical upper limits
Date
2012-11-30T09:17:45Z (13 years ago)
From
Yoichi Yatsu at Tokyo Tech. <yatsu@hp.phys.titech.ac.jp>
T. Yoshii, R. Usui, Y.Aoki, S. Kurita, M. Hayashi,
Y. Saito, Y. Yatsu, and N. Kawai (Tokyo Tech) report
on behalf of the MITSuME collaboration:
We observed GRB 121128A ( Oates et al., GCN Circular #14007) 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 was started on 2012-11-28 08:49:50 UT ( ~13453 sec
after the burst).
We detected the previously reported afterglow ( Oates et al., GCN
Circular #14007)
in Ic band. The results of photometry (3sigma upper limits) are listed below.
The photon flux were calibrated against GSC2.3 catalog.
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------
14491 09:07:08 1800 > 19.4 > 19.1
17.92+/-0.14
-------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst [sec]
T-EXP: Total Exposure time [sec]
GCN Circular 14019
Subject
GRB 121128A: optical observation in Mondy observatory
Date
2012-11-29T17:50:57Z (13 years ago)
From
Alina Volnova at SAI MSU <alinusss@gmail.com>
A.Volnova (SAI MSU), E. Klunko (ISTP), A. Pozanenko (IKI) on behalf of
larger GRB follow up collaboration report:
We observed the field of the Swift GRB 121128A (Oates et al., GCN 14007)
with AZT-33IK telescope of Sayan observatory (Mondy). We took several
images in R-filter of 60 s exposure on Nov. 28, between (UT) 10:27:30 -
13:43:09 under favorable weather conditions. We detected optical afterglow
(Oates et al., GCN 14007; Japelj et al., GCN 14008) in stacked images. A
photometry of some stacked image in the beginning of our observations and
final stacked image is based on nearby USNO-B1.0 stars:
t_start, T0+ (mid), filter, exp., OT, err
(UT) d s
10:46:51 0.24047 R 10x60 19.95 +/- 0.06
13:00:21 0.34123 R 49x40 20.58 +/- 0.07
The photometry is still preliminary.
GCN Circular 14018
Subject
GRB 121128A: WSRT radio observation
Date
2012-11-28T23:16:59Z (13 years ago)
From
Alexander van der Horst at U of Amsterdam <A.J.vanderHorst@uva.nl>
A.J. van der Horst (University of Amsterdam) reports on behalf
of a large collaboration:
"We observed the position of the GRB 121128A afterglow at 4.9 GHz with
the Westerbork Synthesis Radio Telescope at November 28 11.34 to
21.06 UT, i.e. 6.2 - 16.0 hours after the burst (GCN 14007).
We do not detect a radio source at the position of the optical
counterpart (GCN 14007). The three-sigma rms noise in the map around
that position is 69 microJy per beam. The formal flux measurement for
a point source at the position of the optical counterpart is 59 +/- 23
microJy.
We would like to thank the WSRT staff for quickly scheduling and
obtaining these observations."
GCN Circular 14017
Subject
GRB 121128A: Swift/UVOT Detection
Date
2012-11-28T22:58:50Z (13 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (MSSL-UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 121128A
85 s after the BAT trigger (Oates et al., GCN Circ. 14007). A source consistent
with the XRT position (Osborne et al., GCN Circ. 14015) is detected in the initial
white, v, b and u exposures only. The non-detection in the UV filters is consistent
with the redshift of z=2.2 reported by Gemini North (Tanvir et al., GCN Circ. 14009)
The preliminary UVOT position is:
RA (J2000) = 20:02:24.00 = 300.60000 (deg.)
Dec (J2000) = +54:17:59.1 = 54.29974 (deg.)
with an estimated uncertainty of 0.50 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 85 235 147 16.19 +/- 0.03
v 629 649 19 17.00 +/- 0.23
b 554 573 20 17.51 +/- 0.17
u 298 547 246 17.33 +/- 0.06
w1 679 2173 175 >19.6
m2 654 2496 214 >19.6
w2 605 2447 214 >20.0
The magnitudes in the table are not corrected for the significant Galactic extinction
due to the reddening of E(B-V) = 0.31 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 14016
Subject
GRB 121128A: Swift-XRT refined Analysis
Date
2012-11-28T21:18:04Z (13 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
G. Stratta (ASDC), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh
(PSU), O.M. Littlejohns (U. Leicester), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and
S.R. Oates report on behalf of the Swift-XRT team:
We have analysed 12 ks of XRT data for GRB 121128A (Oates et al. GCN
Circ. 14007), from 66 s to 41.5 ks after the BAT trigger. The data
comprise 108 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 enhanced XRT position for this burst was given by Osborne et
al. (GCN. Circ 14015).
The late-time light curve (from T0+6.9 ks) can be modelled with a
power-law decay with a decay index of alpha=1.67 (+0.16, -0.15).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.43 (+/-0.11). The
best-fitting absorption column is 1.2 (+/-0.4) x 10^22 cm^-2, at a
redshift of 2.2, in addition to the Galactic value of 2.1 x 10^21 cm^-2
(Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.99
(+0.10, -0.09) and a best-fitting absorption column of 1.1 (+0.5, -0.4)
x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 4.1 x 10^-11 (6.4 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 2.1 x 10^21 cm^-2
Intrinsic column: 1.1 (+0.5, -0.4) x 10^22 cm^-2 at z=2.2
Photon index: 1.99 (+0.10, -0.09)
If the light curve continues to decay with a power-law decay index of
1.59, the count rate at T+24 hours will be 3.2 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 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/00539866.
This circular is an official product of the Swift-XRT team.
GCN Circular 14015
Subject
GRB 121128A: Enhanced Swift-XRT position
Date
2012-11-28T20:06:28Z (13 years ago)
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 2286 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 121128A, 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 = 300.60001, +54.29971 which is equivalent
to:
RA (J2000): 20h 02m 24.00s
Dec (J2000): +54d 17' 58.9"
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 Circular 14013
Subject
GRB 121128A: RAPTOR Detection During Gamma-Ray Emitting Interval
Date
2012-11-28T16:42:41Z (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 539866 (Oates, et al., GCN 14007). Our narrow-field
RAPTOR-S telescope located in Los Alamos, NM, began imaging at 05:06:12.6 UT,
35.4 s after the Swift BAT trigger and during the period that the BAT was
still detecting gamma-ray emission (Palmer, et al., GCN 14011). Starting
during the gamma-ray emitting interval we detect a brightening counterpart
that ultimately peaks at T+75s with a R-band equivalent magnitude of
approximately 13.9 before beginning to fade. Our unfiltered images are
calibrated to the USNO-B1 R-band.
GCN Circular 14012
Subject
GRB 121128A: Fermi GBM observation
Date
2012-11-28T14:42:17Z (13 years ago)
From
Sinead McGlynn at Excellence Cluster/TUM <smcglynn@tum.de>
Sinead McGlynn (TUM/MPE)
reports on behalf of the Fermi GBM Team:
"At 05:05:50.96 UT on 28 Nov 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 121128A (trigger 375771953/121128212)
which was also detected by the Swift/BAT and UVOT
(Oates et al. 2012, GCN 14007).
The GBM on-ground location is consistent with the Swift UVOT position.
The angle from the Fermi LAT boresight is 83 degrees.
The GBM light curve shows two bright pulses
with a duration (T90) of about 17s (50-300 keV).
The time-averaged spectrum from T0-5.1 s to T0+27.6 s is
best fit by a Band function with Epeak = 62.2 +/- 4.6 keV,
alpha = -0.80 +/- 0.12, and beta = -2.41 +/- 0.10.
The event fluence (10-1000 keV) in this time interval is
(1.04 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+7.9 s in the 10-1000 keV band
is 17.9 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 14011
Subject
GRB 121128A, Swift-BAT refined analysis
Date
2012-11-28T14:32:00Z (13 years ago)
From
Hans Krimm at NASA-GSFC <hans.a.krimm@nasa.gov>
D. M. Palmer (LANL),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),C. B. Markwardt (GSFC), S. R. Oates (UCL-MSSL),
T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):
Using the data set from T-119 to T+195 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 121128A (trigger #539866)
(Oates, et al., GCN Circ. 14007). The BAT ground-calculated position is
RA, Dec = 300.589, 54.301 deg which is
RA(J2000) = 20h 02m 21.3s
Dec(J2000) = +54d 18' 02.6"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 88%. The mask-weighted light curve shows a complex,
multi-peaked structure. The burst began with a faint precursor at ~T-4 sec.
The main emission started at ~T+10 sec, peaked at T+22 sec and continued
until just after T+40 sec, with weak emission extending out to ~T+70 sec.
T90 (15-350 keV) is 23.3 +- 1.6 sec (estimated error including systematics).
The time-averaged spectrum from T-0.00 to T+41.69 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index 1.32 +- 0.18,
and Epeak of 64.5 +- 6.8 keV (chi squared 33.43 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 6.9 +- 0.4 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+21.68 sec in the 15-150 keV band is
12.9 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index
of 1.86 +- 0.04 (chi squared 62.32 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/539866/BA/
GCN Circular 14010
Subject
Konus-Wind observation of GRB 121128A
Date
2012-11-28T12:12:07Z (13 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:
The long-duration soft GRB 121128A
(Swift-BAT trigger #539866: Oates et al., GCN 14007)
triggered Konus-Wind at T0=18353.307s UT (05:05:53.307)
The burst light curve shows a multi-peaked structure with
a total duration of ~30 s.
The emission is seen up to 6 MeV.
As observed by Konus-Wind, the burst
had a fluence of (7.0 � 0.6)x10-6 erg/cm2,
and a 64-ms peak flux, measured from T0+5.568 s,
of (2.05 � 0.15)x10-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst (measured T0 to T0+16.640 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.94 � 0.14,
the high energy photon index beta = -3.36 � 0.48,
the peak energy Ep = 76 � 4 keV,
chi2 = 82.6/87 dof.
The spectrum at the maximum count rate (measured T0 to T0+8.848 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = +0.87 � 0.13,
the high energy photon index beta = -3.32 � 0.46,
the peak energy Ep = 87 � 4 keV,
chi2 = 69.4/60 dof.
Assuming the Gemini North redshift of z=2.20 (Tanvir et al., GCN 14009)
and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27,
Omega_Lambda = 0.73:
the isotropic energy release E_iso is (8.2 � 0.7)x10^52 erg,
the isotropic peak luminosity L_iso_max is (7.7 � 0.6)x10^52 erg/s,
and Ep_rest is (243 � 13) keV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB121128_T18353/
All the quoted results are preliminary.
GCN Circular 14009
Subject
GRB 121128A - Gemini North redshift
Date
2012-11-28T07:46:48Z (13 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), T. Matulonis (Gemini)
report on behalf of a larger collaboration:
We observed the counterpart of GRB 121128A (Oates et al. GCN 14007;
Japelj et al. GCN 14008) with the GMOS-N spectrograph at Gemini-North,
beginning at Nov 28 2012 06:06 UT, approximately 1hr post-burst.
The afterglow is well detected and our provisional reduction shows a
series of absorption lines of AlII, FeII, CIV, SiII, SiIV with a common
redshift of z=2.20.
GCN Circular 14008
Subject
GRB 121128A: FTN optical afterglow confirmation
Date
2012-11-28T07:11:25Z (13 years ago)
From
Jure Japelj at U. of Ljubljana,Slovenia <jure.japelj@fmf.uni-lj.si>
J. Japelj (U. Ljubljana), N.R. Tanvir (U. Leicester), C. Guidorzi
(U. Ferrara) report on behalf of a large collaboration report:
The 2-m Faulkes Telescope North automatically began observing
GRB 121128A (Oates et al. GCN Circ. 14007) on November 28 2012,
05:07:51 UT corresponding to 134 seconds post burst trigger. We confirm
the presence of a fading source at the optical afterglow candidate position
reported by Oates et al. GCN Circ. 14007. In the first 10 s exposure,
we measure a preliminary R magnitude of 14.5 +- 0.1, calibrated against
nearby USNO-B1 stars.
The candidate was discovered automatically by the LT-TRAP pipeline.
GCN Circular 14007
Subject
GRB 121128A: Swift detection of a burst with an optical counterpart
Date
2012-11-28T05:18:00Z (13 years ago)
From
Samantha Oates at MSSL <sro@mssl.ucl.ac.uk>
S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC),
H. A. Krimm (CRESST/GSFC/USRA), N. P. M. Kuin (UCL-MSSL),
C. B. Markwardt (NASA/GSFC), K. L. Page (U Leicester),
M. H. Siegel (PSU) and M. Stamatikos (OSU/NASA/GSFC) report on behalf
of the Swift Team:
At 05:05:37 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121128A (trigger=539866). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 300.583, +54.321 which is
RA(J2000) = 20h 02m 20s
Dec(J2000) = +54d 19' 17"
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 40 sec. The peak count rate
was ~20,000 counts/sec (15-350 keV), at ~20 sec after the trigger.
The XRT began observing the field at 05:06:54.3 UT, 77.2 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 300.60067, 54.30060 which
is equivalent to:
RA(J2000) = 20h 02m 24.16s
Dec(J2000) = +54d 18' 02.2"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 82 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 2.08
x 10^21 cm^-2 (Kalberla et al. 2005).
The initial flux in the 2.5 s image was 1.58e-09 erg cm^-2 s^-1 (0.2-10
keV).
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) = 20:02:24.01 = 300.60004
DEC(J2000) = +54:17:59.2 = 54.29977
with a 90%-confidence error radius of about 0.61 arc sec. This position is 5.5
arc sec. from the center of the XRT error circle. The estimated magnitude is
16.11 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.31.
Burst Advocate for this burst is S. R. Oates (sro 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.)