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GCN Circular 9551

Subject
GRB 090621B: Swift-BAT refined analysis
Date
2009-06-22T13:08:54Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), P.A. Curran (MSSL-UCL), E. E. Fenimore (LANL),
N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
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+963 sec from the recent telemetry downlink,
we report further analysis of BAT short hard burst GRB 090621B (trigger #355359)
(Curran, et al., GCN Circ. 9545).  The BAT ground-calculated position is
RA, Dec = 313.455, 69.034 deg, which is 
   RA(J2000)  =  20h 53m 49.3s 
   Dec(J2000) = +69d 02' 02.9" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.
 
The mask-weighted light curve shows a single peak starting a ~T+0 sec
and ending at ~T+0.2 sec.  There is a 2.5-sigma hint of extended emission
from ~T+150 to ~T+240 sec.  T90 (15-350 keV) is 0.14 +- 0.04 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-0.028 to T+0.148 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.82 +- 0.23.  The fluence in the 15-150 keV band is 7.0 +- 1.0 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band
is 3.9 +- 0.5 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/355359/BA/
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