[vsnet-grb-info 7385] GRB 090308: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8949
SUBJECT: GRB 090308: Swift-BAT refined analysis
DATE:    09/03/08 21:02:11 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), E. E. Fenimore (LANL),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), 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 090308 (trigger #345777)
(Evans, et al., GCN Circ. 8948).  The BAT ground-calculated position is
RA, Dec = 183.545, -48.754 deg, which is 
   RA(J2000)  =  12h 14m 10.7s 
   Dec(J2000) = -48d 45' 13.8" 
with an uncertainty of 3.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 89%.
 
The mask-weighted light curve shows a single peak starting at ~T-10 sec,
peaking at ~T+30 sec, and ending at ~T+65 sec.  T90 (15-350 keV) is
48 +- 22 sec (estimated error including systematics).
 
The time-averaged spectrum from T+4.0 to T+52.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.33 +- 0.37.  The fluence in the 15-150 keV band is 2.6 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+27.50 sec in the 15-150 keV band
is 0.1 +- 0.0 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/345777/BA/