GCN Circular 9756
Subject
GRB 090809: Swift-BAT refined analysis
Date
2009-08-10T02:07:52Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
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),
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-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090809 (trigger #359530)
(Markwardt, et al., GCN Circ. 9754). The BAT ground-calculated position is
RA, Dec = 328.665, -0.083 deg which is
RA(J2000) = 21h 54m 39.5s
Dec(J2000) = -00d 04' 58.0"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.
The mask-weighted light curve shows a single, roughly triangularly shaped
peak starting at ~T-1 sec, peaking at ~T+3 sec, and ending at ~T+9 sec.
T90 (15-350 keV) is 5.4 +- 1.3 sec (estimated error including systematics).
The time-averaged spectrum from T-1.0 to T+6.4 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.34 +- 0.24. The fluence in the 15-150 keV band is 3.4 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.26 sec in the 15-150 keV band
is 1.1 +- 0.2 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/359530/BA/