TITLE:   GCN CIRCULAR
NUMBER:  9263
SUBJECT: GRB 090426: Swift-BAT refined analysis
DATE:    09/04/26 20:40:16 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

G. Sato (ISAS), 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), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090426 (trigger #350479)
(Cummings, et al., GCN Circ. 9254).  The BAT ground-calculated position is
RA, Dec = 189.082, 32.978 deg, which is 
   RA(J2000)  =  12h 36m 19.7s 
   Dec(J2000) = +32d 58' 40.6" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 32%.

The mask-weighted light curve shows a few overlapping peaks starting 
at ~T-0.1 sec, peaking at T+0.5 sec, and ending at ~T+1.5 sec.
T90 (15-350 keV) is 1.2 +- 0.3 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.0 to T+1.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.93 +- 0.22.  The fluence in the 15-150 keV band is 1.8 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.03 sec in the 15-150 keV band
is 2.4 +- 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/350479/BA/