GCN Circular 8986
Subject
GRB 090313: Swift-BAT refined analysis
Date
2009-03-13T13:48:31Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), J. Mao (INAF-OAB), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), 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 recent telemetry downlinks,
we report further analysis of BAT GRB 090313 (trigger #346386)
(Mao, et al., GCN Circ. 8980). The BAT ground-calculated position is
RA, Dec = 198.400, 8.086 deg, which is
RA(J2000) = 13h 13m 36.0s
Dec(J2000) = +08d 05' 10.7"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 15%.
The mask-weighted light curve shows emission starting before T-100 sec
at which time the burst location came into the BAT FOV during a pre-programmed
target slew. BAT triggered on the peak starting at ~T-20 sec, peaking
at ~T+10 sec, and ending at ~T+90 sec. T90 (15-350 keV) is 78 +- 19 sec
(estimated error including systematics).
The time-averaged spectrum from T-21.3 to T+66.6 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.91 +- 0.29. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+4.86 sec in the 15-150 keV band
is 0.8 +- 0.3 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/346386/BA/