[vsnet-grb-info 6639] GRB 080916A, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8243
SUBJECT: GRB 080916A, Swift-BAT refined analysis
DATE:    08/09/16 17:06:23 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

W. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), K. McLean (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU),
H. Ziaeepour (UCL-MSSL)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 080916A (trigger #324895)
(Ziaeepour, et al., GCN Circ. 8237).  The BAT ground-calculated position is
RA, Dec = 336.289, -57.026 deg, which is 
   RA(J2000)  =  22h 25m 09.3s 
   Dec(J2000) = -57d 01' 33.7" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.
 
The mask-weighted light curve shows two overlapping FRED peaks
starting at ~T-3 sec and ending at ~T+100 sec.
T90 (15-350 keV) is 60 +- 7 sec (estimated error including systematics).
 
The time-averaged spectrum from T-2.4 to T+88.6 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.17 +- 0.21, 
and Epeak of 94.6 +- 23.0 keV (chi squared 48.0 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 4.0 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+1.25 sec in the 15-150 keV band is
2.7 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.63 +- 0.05 (chi squared 64.5 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/324895/BA/