TITLE:   GCN CIRCULAR
NUMBER:  7992
SUBJECT: GRB 080721, Swift-BAT refined analysis
DATE:    08/07/21 15:19:27 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), K. McLean (GSFC/UMD),
D. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+750 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 080721 (trigger #317508)
(Marshall, et al., GCN Circ. 7988).  The BAT ground-calculated position is
RA, Dec = 224.481, -11.709 deg, which is 
   RA(J2000)  =  14h 57m 55.4s 
   Dec(J2000) = -11d 42' 33.3" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 4%.
 
The mask-weighted light curve shows approximately six peaks.  The first starts
at ~T-11 sec and peaks at ~T-7 sec.  The second and third peaks are much 
brighter.  They peak at ~T+1 and ~T+7 sec.  The remaining peaks are much smaller
and stretch out to ~T+370 sec.  T90 (15-350 keV) is 16.2 +- 4.5 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-2.6 to T+25.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.11 +- 0.08.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T-0.16 sec in the 15-150 keV band
is 20.9 +- 1.8 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/317508/BA/