TITLE:   GCN CIRCULAR
NUMBER:  10972
SUBJECT: GRB 100724A: Swift-BAT refined analysis
DATE:    10/07/24 15:12:20 GMT
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/