GRB 100724A
GCN Circular 10968
Subject
GRB 100724A: Swift detection of a burst
Date
2010-07-24T01:04:32Z (15 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
C. B. Markwardt (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), J. M. Gelbord (PSU),
S. T. Holland (CRESST/USRA/GSFC), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU),
M. Stamatikos (OSU/NASA/GSFC), C. A. Swenson (PSU),
E. Troja (NASA/GSFC/ORAU) and T. N. Ukwatta (GSFC/GWU) report on
behalf of the Swift Team:
At 00:42:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 100724A (trigger=429868). Swift slewed immediately to the burst.
The BAT on-board calculated location is RA, Dec 194.566, -11.121 which is
RA(J2000) = 12h 58m 16s
Dec(J2000) = -11d 07' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a double peak structure
with a duration of about 70 sec. The peak count rate
was ~3000 counts/sec (15-350 keV), at ~0.5 sec after the trigger.
The XRT began observing the field at 00:43:48.1 UT, 88.9 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 194.5434, -11.1027
which is equivalent to:
RA(J2000) = 12h 58m 10.41s
Dec(J2000) = -11d 06' 09.7"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 104 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 in excess of the Galactic value (3.35e+20
cm^-2, Kalberla et al. 2005), with an excess column of 9.7
(+13.63/-5.98) x 10^20 cm^-2 (90% confidence).
UVOT took a finding chart exposure of nominal 250 seconds with the U filter
starting 304 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. Data from the 2.7'x2.7' sub-image are
not available at this time. 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 0.04.
Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt 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 Circular 10969
Subject
GRB 100724A, GROND detection of an afterglow candidate
Date
2010-07-24T01:21:28Z (15 years ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
F. Olivares E., J. Greiner, P. Afonso (all MPE Garching),
and S. Klose (TLS Tautenburg) report on behalf of the GROND team:
GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted
at the 2.2m ESO/MPI telescope on La Silla, started follow-up observations
of GRB 100724A (Swift trigger 429868; Markwardt et al. 2010, GCN 10968) on
July 24 at 0:45 UT (about 3 min after the trigger).
Within the revised 2.4 arcsec XRT error circle we find an afterglow
candidate at position RA, Dec (J2000) = 12:58:10.4, -11:06:09, visible
in all bands. We conclude that the redshift is less than 3.5.
Observations are ongoing.
GCN Circular 10970
Subject
GRB 100724A: fading afterglow seen with GROND
Date
2010-07-24T02:16:21Z (15 years ago)
From
Sylvio Klose at TLS Tautenburg <klose@tls-tautenburg.de>
F. Olivares E., J. Greiner, P. Afonso (all MPE Garching), and S. Klose
(TLS Tautenburg), report on behalf of the GROND team:
The afterglow candidate reported by Olivares et al. (GCN 10969) is clearly
fading. Between mid-times of 00:49 UT and 01:14 UT the object faded by 1.3
magnitudes, corresponding to a power-law decay index of about 0.7. We
therefore confirm this object to be the afterglow of GRB 100724A.
GCN Circular 10971
Subject
GRB 100724A: X-shooter redshift
Date
2010-07-24T06:55:35Z (15 years ago)
From
Antonio Deugarte at IAA-CSIC <deugarte@iaa.es>
C. C. Thoene, A. de Ugarte Postigo (INAF-OAB), P. Vreeswijk (Univ.
Iceland), P. D'Avanzo, S. Covino (INAF-OAB), J. P. U. Fynbo (DARK/NBI) and
N. Tanvir (Univ. Leicester) report on behalf of the X-shooter
collaboration
We observed the optical afterglow of GRB 100724A (Markwardt et al., GCN
10968, Olivares et al., GCN 10969, 10970) with X-shooter at the VLT in RRM
mode on July 24, 2010, starting at 00:53 UT (11 min after the burst).
We detect several absorption lines including Fe II 2344, 2383, 2586, 2600,
the Mg II doublet (2796, 2803) and Mg I 2852 at a common redshift of 1.288
which we suggest to be the redshift of the GRB. The wavelength calibration
was obtained from archival files and is therefore considered preliminary.
We thank the Paranal staff for performing the observations, in particular
Lorenzo Monaco and Andres Pino.
GCN Circular 10972
Subject
GRB 100724A: Swift-BAT refined analysis
Date
2010-07-24T15:12:20Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+644 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 100724A (trigger #429868)
(Markwardt, et al., GCN Circ. 10968). The BAT ground-calculated position is
RA, Dec = 194.569, -11.095 deg, which is
RA(J2000) = 12h 58m 16.5s
Dec(J2000) = -11d 05' 41.7"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.
The mask-weighted light curve shows several overlapping peaks starting
at T+0.0 sec and ending at T+4.0 sec. There is a weak roughly exponential tail
extending out to ~T+20 sec. T90 (15-350 keV) is 1.4 +- 0.2 sec (estimated error
including systematics). The initial description of the lightcurve given
in GCN Circ 10968 as being 70 sec long was confused by the nearly simultaneous,
but different burst detected by Fermi. The BAT mask-weighted lightcurve
clearly shows that the 100724A burst is only single episode around T_zero.
There is nothing in the mask-weighted lightcurve in the T+40 to T+70sec range.
The time-averaged spectrum from T+0.1 to T+1.6 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.92 +- 0.21. The fluence in the 15-150 keV band is 1.6 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.09 sec in the 15-150 keV band
is 1.9 +- 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/429868/BA/
GCN Circular 10973
Subject
GRB 100724A: Swift/UVOT observations
Date
2010-07-24T15:21:51Z (15 years ago)
From
Craig Swenson at PSU/Swift <cswenson@astro.psu.edu>
C. A. Swenson (PSU) and C. B. Markwardt (CRESST/GSFC/UMD) report
on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 100724A
74s after the BAT trigger (Markwardt et al., GCN 10968). We detect a
source at the position of the detected X-ray source (Markwardt et al.,
GCN 10968) and the location reported by GROND (Olivares et al., GCN
10969). The source is clearly fading in the UVOT white filter between
the first finding chart and a later observation.
The magnitudes and 3-sigma upper limits using the UVOT photometric
system (Poole et al., 2008, MNRAS, 383, 627) for finding chart exposures
(FC) and the summed images are:
Filter T_start T_stop Exp(s) Magnitude/3-sigma upper limit
----------------------------------------------------------------------
white (FC) 92 242 147 18.46 � 0.11
white 584 775 39 > 19.71
u (FC) 304 554 246 18.54 � 0.15
u 706 726 19 18.17 � 0.37
v 74 1050 60 > 18.31
b 559 751 39 > 18.99
uvw1 682 702 19 > 17.96
uvm2 658 850 39 > 18.19
uvw2 609 1034 58 > 18.97
The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight of E_(B-V) = 0.043 mag
(Schlegel, et al., 1998, ApJS, 500, 525).
GCN Circular 10974
Subject
GRB 100724A: Enhanced Swift-XRT position
Date
2010-07-24T16:03:15Z (15 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.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 6782 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 100724A, 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 = 194.54312, -11.10263 which is equivalent
to:
RA (J2000): 12h 58m 10.35s
Dec (J2000): -11d 06' 09.5"
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.
GCN Circular 10975
Subject
GRB 100724A: Swift XRT refined analysis
Date
2010-07-24T18:32:29Z (15 years ago)
From
Boris Sbarufatti at INAF-OAB/IASFPA <boris.sbarufatti@brera.inaf.it>
V. Mangano (INAF IASF-PA), B. Sbarufatti (INAF OAB/INAF IASF-PA) and
C. B. Markwardt (CRESST/GSFC/UMD) report on behalf of the Swift-XRT team:
We have analysed 10 ks of XRT data for GRB 100724A (Markwardt et al.
GCN Circ. 10968), from 96 s to 25.1 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. The light curve can be
modelled with a broken power-law decay with an initial decay index of
alpha1=0.3 (+/-0.1) , a break at T+525 (+/-90) s and a final decay index of
alpha2=1.07 (+/-0.03).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.98 (+0.20, -0.19).
The best-fitting absorption column is consistent with the Galactic value
of 3.4 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 4.8 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1.
If the light curve continues to decay with a power-law decay index of
1.1, the count rate at T+24 hours will be 2.4e-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of
1.1 x 10^-13 (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/00429868.
This circular is an official product of the Swift-XRT team.
GCN Circular 10976
Subject
GRB 100724A: Swift/BAT spectral lag results
Date
2010-07-24T22:31:45Z (15 years ago)
From
Tilan Ukwatta at GSFC/GWU <tilan.ukwatta@gmail.com>
T. N. Ukwatta (GWU/GSFC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC),
C. B. Markwardt (CRESST/GSFC/UMD), J. Norris (U. Denver),
and T. Sakamoto (GSFC/UMBC) (for the Swift-BAT team):
For GRB 100724A (Markwardt et al GCN 10968), the spectral lag analysis
of the mask-weighted data from T-0.5 sec to T+2 sec yields a lag
of 316 +/- 82 msec for the 25-50 to 50-100 keV bands using light
curve binning of 64 msec. This relatively large observed lag value
puts this burst in the long burst category.
The observed T90 (1.4 +/- 0.2 sec; Swift/BAT 15-350 keV,
Markwardt et al., GCN 10972) value is in the middle of the
the soft/long bimodal distribution. The power-law fit to the
BAT spectrum gives index (PLI) of 1.92 +/- 0.21 (Markwardt et al.,
GCN 10972), which is in the middle of the Long GRB PLI distribution
and in the soft side tail of the Short GRB PLI distribution.
In summary, the observed T90 value for GRB 100724A is inconclusive.
The relatively large spectral lag value and soft spectrum points
towards long soft burst. Our conclusion is that this burst
is likely to be in the long burst category. Further observations
are encouraged to characterize the host galaxy.