TITLE:   GCN CIRCULAR
NUMBER:  8986
SUBJECT: GRB 090313: Swift-BAT refined analysis
DATE:    09/03/13 13:48:31 GMT
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/