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GCN Circular 8222

Subject
GRB 080913, Swift-BAT refined analysis
Date
2008-09-13T16:07:01Z (15 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <jayc@milkyway.gsfc.nasa.gov>
M. Stamatikos (GSFC/ORAU),  S. D. Barthelmy (GSFC),  W. Baumgartner 
(GSFC/UMBC),
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),
P. Schady (MSSL-UCL),  J. Tueller (GSFC),  T. Ukwatta (GWU)

(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 080913 (trigger #324561) (Schady, 
et al.,
GCN Circ. 8217).  The BAT ground-calculated position is
RA, Dec = 65.741, -25.127 deg which is
  RA(J2000)  =  04h 22m 57.9s
  Dec(J2000) = -25d 07' 38.6"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 39%.

The mask-weighted light curve shows multiple overlapping peaks, somewhat
smooth in character.  T90 (15-350 keV) is 8 +- 1 sec (estimated error
including systematics).

The time-averaged spectrum from T-3.8 to T+5.2 sec is best fit by a 
power law
with an exponential cutoff.  This fit gives a photon index 0.46 +- 0.70,
and Epeak of 93.1 +- 56.1 keV (chi squared 38.53 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 5.6 +- 0.6 x 10-07 
erg/cm2
and the 1-sec peak flux measured from T+0.11 sec in the 15-150 keV band is
1.4 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.36 +- 0.15 (chi squared 44.56 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/324561/BA/
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