GCN Circular 8936
Subject
GRB 090305, Swift-BAT refined analysis
Date
2009-03-05T18:15:07Z (15 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL),
N. Gehrels (GSFC), C. B. Markwardt (GSFC/UMD), K. McLean (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-61 to T+242 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 090305 (trigger #345127)
(Beardmore et al., GCN 8932). The BAT ground-calculated position is
RA, Dec = 241.764, -31.572 deg which is
RA(J2000) = 16h 07m 03.5s
Dec(J2000) = -31d 34' 20.9"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
This position is 1.3 arcmin from the optical afterglow reported by
Cenko et al. (GCN Circ 8933). The partial coding was 50%.
The lightcurve consists of two pulses, the first about 0.08 seconds
long and the second about 0.28 seconds long. T90 (15-350 keV) is
0.4 +- 0.1 sec (estimated error including systematics). There was
very little emission seen in the BAT low energy band, 15-25 keV.
The time-averaged spectrum from T+0.0 to T+0.4 sec is best fit by a
simple power-law model. The power law index of the time-averaged
spectrum is 0.86 +- 0.33. The fluence in the 15-150 keV band is
7.5 +- 1.3 x 10^-08 erg/cm2. The 1-sec peak photon flux measured from
T-0.29 sec in the 15-150 keV band is 1.9 +- 0.4 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/345127/BA/