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GCN Circular 9775

Subject

GRB 090812 Swift-BAT Refined Analysis

Date

2009-08-12T15:09:27Z (15 years ago)

From

Michael Stamatikos at OSU/GSFC <michael.stamatikos-1@nasa.gov>

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), 
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU/NASA/GSFC),
J. Tueller (GSFC), T. N. Ukwatta (GWU) on behalf of 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 090812 (trigger #359711)
(Stamatikos, et al., GCN Circ. 9768Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 353.200, -10.609 deg which is 
   RA(J2000)  =  23h 32m 47.9s 
   Dec(J2000) = -10d 36' 34.1" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.
 
The burst starts at ~T-4 sec and ends at ~T+120 sec, with 3 peaks at ~T+5 sec,
 ~T+27 sec and ~T+55 sec, respectively. T90 (15-350 keV) is 66.7 +- 14.7 sec 
(estimated error including systematics).
 
The time-averaged spectrum from T-5.4 to T+113.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.24 +- 0.05.  The fluence in the 15-150 keV band is 5.8 +- 0.2 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+26.82 sec in the 15-150 keV band
is 3.6 +- 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/359711/BA/.

[GCN OPS NOTE(13aug09):  Per author's request, the "080912" was changed
to "090812" in the Subject line.]