GCN Circular 6732
Subject
GRB 070809, Swift-BAT refined analysis
Date
2007-08-10T01:46:26Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
C. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), D. Palmer (LANL),
A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-120 to T+183 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 070809 (trigger #287344)
(Marshall, et al., GCN Circ. 6728). The BAT ground-calculated position is
RA, Dec = 203.767, -22.119 deg which is
RA(J2000) = 13h 35m 4.2s
Dec(J2000) = -22d 7' 7"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 74%.
The mask-weighted light curve consists of a single peak starting at ~T-0.3
and ending at ~T+1.2 sec. T90 (15-350 keV) is 1.3 +- 0.1 sec (estimated error
including systematics).
The time-averaged spectrum from T-0.4 to T+1.1 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.69 +- 0.22. The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.08 sec in the 15-150 keV band
is 1.2 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level. We note that the T90-hardness_ratio for this burst falls in between
the SHB and LSB clusters in the T90-HR scatter plot for Swift-BAT.