GRB 121024A
GCN Circular 13931
Subject
GRB 121024A: LOAO RIzY Observation
Date
2012-10-30T11:36:05Z (14 years ago)
From
Minsung Jang at Seoul National U <rigel103@snu.ac.kr>
M. Jang, M. Im (SNU), and Y. Urata (NCU), on behalf of a larger collaboration
We observed GRB 121024A in RIzY-bands starting at UT 10:52:00, 2012-10-24,
~ 9 hrs after the BAT trigger (Baumgartner et al, GCN 10484),
using the 1.0m telescope at Mt.Lemmon in Arizona, U.S.
We do not detect the GRB afterglow in all bands within the error circle
of the enhanced XRT position (Evans et al.,GCN 13892).
We estimate the 3-sigma limiting magnitude of the afterglow to be
R ~ 20.0 at the midpoint time (~T0+9.3 hrs)
by calibrating it against seven USNO-B1 stars with R2 magnitudes
without the galactic extinction correction.
We thank the LOAO operator, J. Yoon, for performing the observation.
GCN Circular 13928
Subject
GRB 121024A: SMARTS optical/IR afterglow observations
Date
2012-10-29T21:00:20Z (14 years ago)
From
Bethany Cobb at GWU <bcobb@gwu.edu>
B. E. Cobb (GWU), reports:
Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained
optical/IR imaging of the error region of GRB 121024A (GCN 13886,
Pagani et al.) over several epochs (with mid-exposure times of
2012-10-24 03:51 UT, 06:10 UT, 08:12 UT and 2012-10-25 06:53 UT).
For each epoch, several dithered images were obtained with
total summed exposure times of 15 min in V and I and 12 min in
J and K. For the final epoch, total exposure times were
36 min in I and 30 min in J.
The fading afterglow of GRB 121024A (e.g. GCN 13887, Klotz et al.; GCN
13888, Jelinek et al.; GCN 13891, Knust et al.) was detected with the
following magnitudes (or 3-sigma limits):
mid-exposure
time
(hours) I mag J mag K mag
0.90722 18.0 +/- 0.1 16.7 +/- 0.1 15.2 +/- 0.2
3.23611 19.4 +/- 0.1 17.9 +/- 0.1 16.3 +/- 0.2
5.27333 19.8 +/- 0.1 > 18.0 > 16.4
27.95278 > 21.9 > 19.3 ...
(Optical photometry is calibrated against USNO-B1.0 stars
and IR photometry is calibrated against 2MASS stars in the field.)
GCN Circular 13904
Subject
GRB 121024A: optical observations
Date
2012-10-26T08:18:43Z (14 years ago)
From
Shashi Bhushan Pandey at ROTSE <shaship@umich.edu>
S. B. Pandey and Brajesh Kuamr (ARIES Nainital India,
on behalf of larger Indian GRB collaboration).
We observed the GRB 121024A field (Pagani et al., GCN 13886) using
1.04m telescope at ARIES Nainital, starting ~16.9 hours after the
burst (19:49:49 UT, 2012-10-24). Several frames in R_c and I_c
pass-bands were acquired in high air-mass conditions.
In our co-added image (6x300 sec) of R_c band, the optical afterglow
candidate (Knust et al., GCN 13891) is clearly detected. The preliminary
photometry of the co-added frame (calibrated against nearby USNO stars)
estimates the magnitude of the optical afterglow to be 21.1 +- 0.1 mag.
This massage may be cited.
GCN Circular 13903
Subject
GRB 121024A: EVLA Detection
Date
2012-10-26T03:54:19Z (14 years ago)
From
Tanmoy Laskar at Harvard U <tanmoylaskar@gmail.com>
T. Laskar, A. Zauderer, and E. Berger (Harvard) report:
"We observed the position of GRB 121024A (Pagani et al; GCN 13886) with the
EVLA beginning on 2012 Oct 25.3 UT (1.2 days after the burst). At a mean
frequency of 22 GHz, we detect a radio counterpart with a preliminary flux
density of ~ 0.1 mJy consistent with the enhanced Swft/XRT position
(Osborne et al; GCN 13894), the optical position (e.g. Knust et al.; GCN
13891) and the CARMA 3 mm position (Zauderer et al; GCN 13900). Follow-up
observations are planned."
GCN Circular 13901
Subject
GRB 121024A: Swift/UVOT Observations
Date
2012-10-25T20:02:12Z (14 years ago)
From
Stephen Holland at STScI <sholland@stsci.edu>
S. T. Holland (STScI) and C. Pagani (U Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB
121024A starting 158 s after the BAT trigger (Pagani et al., 2012,
GCNC 13886). We continued to detect the optical afterglow until
approximately 10 ks after the BAT trigger. Preliminary UVOT
photometry, and 3-sigma upper limits, for the afterglow is presented
below.
-----------------------------------------------------
Filter TSTART TSTOP Exp Time Mag Err
-----------------------------------------------------
u (fc) 158 408 246 18.43 0.10
-----------------------------------------------------
v 464 483 19 >18.1
b 413 433 19 18.44 0.25
u 538 557 19 >18.5
uvw1 513 533 19 >18.1
uvm2 488 508 19 >17.6
uvw2 439 459 19 >18.1
-----------------------------------------------------
The quoted magnitudes and upper limits have not been corrected for
the Galactic extinction along the line of sight to this burst of
E_{B-V} = 0.09 mag (Schlafly et al. 2011, ApJS, 737, 103). The
photometry is in the UVOT photometric system (Breeveld et al. 2011,
AIP Conf. Proc. 1358, 373).
GCN Circular 13900
Subject
GRB 121024A: CARMA 3mm Detection
Date
2012-10-25T16:43:05Z (14 years ago)
From
Ashley Zauderer at CfA <bevinashley@gmail.com>
B. Zauderer, T. Laskar 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 121024A (Pagani et al; GCN 13886) with
the Combined Array for Research in Millimeter Astronomy beginning 2012
Oct 25.5 (dt=1.4 d after the burst). At a mean frequency of ~85 GHz, we
detect a radio counterpart with a preliminary flux of ~1 mJy within the
enhanced Swft/XRT error circle (Osborne et al; GCN 13894) and consistent
with the optical afterglow (e.g. Knust et al.; GCN 13891).
We thank the CARMA observers and staff for their support. Followup
observations are planned."
GCN Circular 13899
Subject
GRB 121024A: Swift-BAT refined analysis
Date
2012-10-25T14:39:10Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
S. D. Barthelmy (GSFC), T. Sakamoto (AGU), 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), C. Pagani (U Leicester),
D. M. Palmer (LANL), 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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 121024A (trigger #536580)
(Pagani, et al., GCN Circ. 13886). The BAT ground-calculated position is
RA, Dec = 70.481, -12.255 deg, which is
RA(J2000) = 04h 41m 55.5s
Dec(J2000) = -12d 15' 19.1"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.
The mask-weighted light curve shows two overlapping peaks starting
at ~T-9 sec, peaking at ~T-7 and ~T+2 sec, and ending at ~T+6 sec
with a long low tail out to ~T+70 sec (and possibly out to ~T+130 sec).
T90 (15-350 keV) is 69 +- 32 sec (estimated error including systematics).
The time-averaged spectrum from T-8.27 to T+75.73 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.41 +- 0.22. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.73 sec in the 15-150 keV band
is 1.3 +- 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/536580/BA/
GCN Circular 13898
Subject
GRB 121024A: GMG optical observation
Date
2012-10-25T13:49:44Z (14 years ago)
From
Xiao-hong Zhao at Yunnan Obs <zhaoxiaohong78@gmail.com>
X.-H. Zhao (YNAO), J.-R. Mao (KASI/YNAO), J.-M. Bai
(YNAO) report on behalf of a larger collaboration:
We observed the field of GRB 121024A (Pagani et al., GCN 13886) with 2.4m Gao-Mei-Gu (GMG) telescope. Observations
started at 16:30:00 UT on 2012-10-24 (i.e., 13.6 hrs after the burst) and 2x900s R-band images were obtained. The optical afterglow of this burst was clearly detected. The results are as follows:
mid time from trigger (hr) Mag. Err. Exposure time (second)
13.69 20.88 0.1 900
13.81 20.81 0.1 900
We thank the GMG staff, especially Fang Wang, De-Qing Wang and Jian-Duo He for
performing these observations.
GCN Circular 13897
Subject
GRB 121024A: MITSuME Ishigakijima upper limits
Date
2012-10-25T12:20:18Z (14 years ago)
From
Daisuke Kuroda at OAO/NAOJ <dikuroda@oao.nao.ac.jp>
D. Kuroda (OAO, NAOJ), H. Hanayama, T. Miyaji, J. Watanabe (IAO, NAOJ),
K. Yanagisawa (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 121024A (Pagani et al., GCNC 13886)
with the optical three color (g', Rc and Ic) CCD camera attached
to the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory.
The observation started on 2012-10-24 14:30:52 UT (~11.6 h after the burst)
We did not find any new point source within the enhanced XRT circle
(Osborne et al., GCNC 13894) in all the three bands.
We also could not detect the previously reported afterglow
(Klotz et al., GCNC 13887).
Three sigma upper limits of the OT are listed below. We used
GSC2.3 catalog for flux calibration.
T0+[day] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------
0.52401 15:30:47 6060.0 >21.7 >21.4 >20.6
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
GCN Circular 13896
Subject
GRB 121024A: MITSuME Okayama Optical upper limits
Date
2012-10-25T10:54:18Z (14 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 121024A (Pagani et al., GCNC 13886)
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 2012-10-24 13:51:59 UT (~10.9 h after the burst)
We did not find any new point source within the enhanced XRT circle
(Osborne et al., GCNC 13894) in all the three bands.
We also could not detect the previously reported afterglow
(Klotz et al., GCNC 13887).
Three sigma upper limits of the OT are listed below. We used
GSC2.3 catalog for flux calibration.
T0+[day] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------
0.55338 16:13:04 7740.0 >20.1 >20.0 >19.3
------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
GCN Circular 13894
Subject
GRB 121024A: Enhanced Swift-XRT position
Date
2012-10-25T00:58:32Z (14 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 7610 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 121024A, 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 = 70.47208, -12.29052 which is equivalent
to:
RA (J2000): 04h 41m 53.30s
Dec (J2000): -12d 17' 25.9"
with an uncertainty of 1.4 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.
GCN Circular 13893
Subject
GRB 121024A: PAIRITEL NIR Detection
Date
2012-10-24T19:52:45Z (14 years ago)
From
Adam Morgan at U.C. Berkeley <qmorgan@gmail.com>
A. N. Morgan, and J. S. Bloom (UC Berkeley) report:
We observed the field of GRB 121024A (Pagani et al., GCN 13886) with
the 1.3m PAIRITEL located at Mt. Hopkins, Arizona. Observations began
at 2012-Oct-24 07h31m47s UT, ~4.6 hours after the Swift Trigger. In
mosaics (effective exposure time of 0.46 hours) taken simultaneously
in the J, H, and K filters, we detect a source at the optical
afterglow location (Pagani et al., GCN 13886; Klotz et al., GCN 13887;
Jelinek et al., GCN 13888; LaCluyze et al., GCN 13889; Knust et al.
GCN 13891).
The preliminary photometry yields:
post burst
t_mid (hr) exp.(hr) filt mag m_err
6.06 0.46 J >18.4 3sig
6.06 0.46 H 17.1 0.2
6.06 0.46 Ks >16.2 3sig
All magnitudes are given in the Vega system, calibrated to 2MASS. No
correction for Galactic extinction has been made to the above reported
values.
GCN Circular 13892
Subject
GRB 121024A: Swift-XRT refined Analysis
Date
2012-10-24T19:24:10Z (14 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), A. Maselli (INAF-IASFPA), V. Mangano
(INAF-IASFPA), A. Melandri (INAF-OAB), M.C. Stroh (PSU), D.N. Burrows
(PSU), J.A. Kennea (PSU), A.P. Beardmore (U. Leicester) and C. Pagani
report on behalf of the Swift-XRT team:
We have analysed 7.0 ks of XRT data for GRB 121024A (Pagani et al. GCN
Circ. 13886), from 82 s to 23.5 ks after the BAT trigger. The data
comprise 242 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 = 70.47078, -12.29099 which
is equivalent to:
RA (J2000): 04 41 52.99
Dec(J2000): -12 17 27.6
with an uncertainty of 3.5 arcsec (radius, 90% confidence).
The late-time light curve (from T0+3.9 ks) can be modelled with a
power-law decay with a decay index of alpha=0.89 (+/-0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.15 (+/-0.08). The
best-fitting absorption column is 8.0 (+2.1, -2.0) x 10^21 cm^-2, at a
redshift of 2.298, in addition to the Galactic value of 5.4 x 10^20
cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index
of 1.96 (+/-0.13) and a best-fitting absorption column of 7.1 (+4.0,
-3.6) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV
flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (4.7
x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 5.4 x 10^20 cm^-2
Intrinsic column: 7.1 (+4.0, -3.6) x 10^21 cm^-2 at z=2.298
Photon index: 1.96 (+/-0.13)
If the light curve continues to decay with a power-law decay index of
0.89, the count rate at T+24 hours will be 0.016 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.8 x
10^-13 (7.3 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/00536580.
This circular is an official product of the Swift-XRT team.
GCN Circular 13891
Subject
GRB 121024A: GROND Detection of the Optical/NIR Afterglow
Date
2012-10-24T11:31:10Z (14 years ago)
From
Patricia Schady at MPE/Swift <pschady@mpe.mpg.de>
F. Knust, P. Schady and J. Greiner (all MPE Garching) report on behalf
of the GROND team
We observed the field of GRB 121024A (Pagani et al., GCN 13886)
simultaneously in g'r'i'z' with GROND (Greiner et al. 2008, PASP, 120,
405) mounted on the 2.2 m MPG/ESO telescope at La Silla Observatory
(Chile).
Due to clouds, observations only started at 05:53 UT no 24th October,
3 hours after the GRB trigger, and continued until the end of the
night, 3.8 hours later. They were performed at an average seeing of
1.4" and at an average airmass of 1.1.
We find a single point source within the 0.8 arcsec Swift/UVOT error
circle reported by Pagani et al. (GCN 13886) at
RA (J2000.0) = 04:41:53.30
Dec (J2000.0) = -12:17:26.5
with an uncertainty of 0.4" in each coordinate.
Based on the first 142 sec integration in g'r'i'z' and 240 sec
integration in JHK taken at a mid-time of 05:58 UT and 05:54 UT in the
optical and NIR respectively, we estimate preliminary magnitudes (all
in AB system) of
g' = 21.0 +/- 0.2 mag
r' = 20.1 +/- 0.2 mag
i' = 19.8 +/- 0.2 mag
z' = 19.5 +/- 0.2 mag
J = 18.7 +/- 0.1 mag
H = 18.4 +/- 0.1 mag
K = 17.9 +/- 0.1 mag
Given magnitudes are calibrated against GROND zeropoints in the
optical, and 2MASS field stars in the NIR, 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 Circular 13890
Subject
GRB 121024A: VLT/X-shooter redshift
Date
2012-10-24T07:10:59Z (14 years ago)
From
Nial Tanvir at U.Leicester <nrt3@star.le.ac.uk>
N. R. Tanvir (U. Leicester), J. P. U. Fynbo (DARK/NBI), A. Melandri (INAF-OAB),
A. J. Levan (U. Warwick), D. Xu (WIS), V. D'Elia (ASDC) report on behalf of
the X-shooter GTO collaboration:
We observed the afterglow of GRB 121024A (Pagani et al. GCN 13886) with the
X-shooter spectrograph at the VLT. Observations began at 04:45 UT, approximately
1.8 hours after the initial detection of the burst. The afterglow is well detected in
the acquisition image, and in the resulting spectrum we see a strong, broad
damped-Lya absorption feature at ~4000A, combined with numerous narrow metal
lines of CIV, SiII, SiIV, FeII, SII and AlII, as well as fine-structure lines associated
with SiII*. These point to a common redshift of z=2.298 for GRB 121024A.
We thank Maja Vuckovic, Giovanni Carraro, Marcelo Lopez and Felipe Gaete
for their assistance in obtaining these observations, and Gianni Marconi
and Gerry Gilmore for kindly allowing the ToO to be performed during their
visitor mode run.
GCN Circular 13889
Subject
Skynet PROMPT/Dolomiti observations of GRB121024A
Date
2012-10-24T05:47:22Z (14 years ago)
From
Aaron LaCluyze at U.North Carolina <lacluyze@email.unc.edu>
A. LaCluyze, J. Haislip, K. Ivarsen, D. Reichart, J. Moore, H. T.
Cromartie, R. Egger, A. Foster, N. Frank, M. Nysewander, A. Oza, E.
Speckhard, A.Trotter, and J. A. Crain report:
Skynet observed the field of GRB121024A (GCN 13886, Swift trigger #536580)
with the PROMPT telescopes located at CTIO in Chile and the 16" Dolomites
Astronomical Observatory telescope (DAO) in Italy beginning ~1 minute after
the burst trigger. We detect the fading optical source reported by Klotz
et al. (GCN #13887) in all observed filters (g',r',i',z' and BRI.)
Further observations are ongoing.
GCN Circular 13888
Subject
GRB 121024A: BOOTES-1B optical detection
Date
2012-10-24T05:03:53Z (14 years ago)
From
Martin Jelinek at Inst.Astrophys.Andalucia,Granada <mates@iaa.es>
Martin Jelinek, Alberto J. Castro-Tirado and Javier Gorosabel
(IAA-CSIC Granada) on behalf of a larger collaboration
report:
"The 0.3m BOOTES-1B robotic telescope located in Huelva
(Spain), observed the optical afterglow of GRB 121024A
(Pagani et al., GCNC 13886; Klotz et al., GCNC 13887).
The observations started 40 minutes after the GRB trigger.
The sum of 20 minutes of unfiltered images with a mean
integration time 54 minutes after the GRB shows the OT
with magnitude roughly 18.2+-0.5."
GCN Circular 13887
Subject
GRB 121024A: TAROT Calern observatory optical detection of a bright counterpart
Date
2012-10-24T03:20:53Z (14 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 121024A detected by SWIFT
(trigger 536580) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.
The observations started 45.0s after the GRB trigger
(13.9s after the notice). The elevation of the field decreased from
32 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 detect a new fading source in the error box given by SWIFT
We detected the candidate couterpart mentioned by Pagani et al. (GCNC 13886)
at the following position (+/- 2 arcsec):
RA(J2000.0) = 04h 41m 53.41s
DEC(J2000.0) -12d 17' 26.9"
OT was R~13.3 betwenn 45.0s and 60s after GRB.
Then the flux decreases.
Observations are continuing.
Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.
N.B. Galactic coordinates are lon=209.4933 lat=-34.2488
and the galactic extinction in R band is about 0.1 magnitude
estimated from D. Schlegel et al. 1998ApJ...500..525S.
This message may be cited.
[GCN OPS NOTE(24oct12): Per author's request, the circular citation
was added and the uncertainty was increased from 1 to 2 arcsec.]
GCN Circular 13886
Subject
GRB 121024A: Swift detection of a burst with an optical counterpart
Date
2012-10-24T03:12:57Z (14 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
C. Pagani (U Leicester), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), C. Gronwall (PSU), J. A. Kennea (PSU),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU) and
T. N. Ukwatta (MSU) report on behalf of the Swift Team:
At 02:56:12 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121024A (trigger=536580). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 70.467, -12.269 which is
RA(J2000) = 04h 41m 52s
Dec(J2000) = -12d 16' 06"
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 ~3500 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 02:57:45.5 UT, 93.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 70.4715, -12.2904 which is equivalent to:
RA(J2000) = +04h 41m 53.16s
Dec(J2000) = -12d 17' 25.4"
with an uncertainty of 5.5 arcseconds (radius, 90% containment). This
location is 78 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 1.10e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 250 seconds with the U filter starting
158 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 04:41:53.28 = 70.47201
DEC(J2000) = -12:17:26.8 = -12.29079
with a 90%-confidence error radius of about 0.78 arc sec. This position is 2.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.38 with a 1-sigma error of about 0.16. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.10.
Burst Advocate for this burst is C. Pagani (cp232 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/too.html.)