TITLE:   GCN CIRCULAR
NUMBER:  10136
SUBJECT: GRB 091104: Swift-BAT refined analysis
DATE:    09/11/04 20:26:56 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
P.A. Curran (MSSL-UCL), 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-239 to T+903 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 091104 (trigger #374875)
(Curran, et al., GCN Circ. 10130).  The BAT ground-calculated position is
RA, Dec = 208.723, 47.391 deg, which is 
   RA(J2000)  =  13h 54m 53.6s 
   Dec(J2000) = +47d 23' 25.8" 
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.
 
The mask-weighted light curve shows a sharp rise at ~T+2, a rather flat top,
and ending at ~T+120 sec.  T90 (15-350 keV) is 99.3 +- 20 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-1.5 to T+120.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.74 +- 0.24.  The fluence in the 15-150 keV band is 7.7 +- 1.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+83.34 sec in the 15-150 keV band
is 0.4 +- 0.1 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/374875/BA/