GCN Circular 9788
Subject
GRB 090813, Swift-BAT refined analysis
Date
2009-08-13T13:55:52Z (15 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (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 (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 090813 (trigger #359884)
(GRB 090813, Cummings et al., GCN Circ. 9781). The BAT
ground-calculated position is RA, Dec = 225.065, 88.571 deg which is
RA(J2000) = 15h 00m 15.6s
Dec(J2000) = +88d 34' 15.8"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 18%.
The mask weighted lightcurve had three main spikes, at T+0, T+1 and
T+6.5 sec, each with a duration of about 1 sec. T90 (15-350 keV) was
7.1 +- 0.6 sec (estimated error including systematics). The three
spikes were progressively softer.
The time-averaged spectrum from T-0.8 to T+7.3 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 1.69 +- 0.12. The fluence in the 15-150 keV band is 1.3 +-
0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T-0.04 sec
in the 15-150 keV band is 8.5 +- 0.6 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/359884/BA/