TITLE:   GCN CIRCULAR
NUMBER:  41321
SUBJECT: GRB 250809A: Swift-BAT refined analysis
DATE:    25/08/11 18:09:12 GMT
FROM:    D. R. Sadaula at NASA GSFC <dev.r.sadaula@nasa.gov>

D. Sadaula (GSFC/UMBC), S. D. Barthelmy (GSFC), 
R. Gupta (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC),
T. Sakamoto (AGU) (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 250809A (trigger #1340954)
(Parsotan, et al., GCN Circ. 41303).  The BAT ground-calculated position is
RA, Dec = 233.034, -53.314 deg which is 
   RA(J2000)  =  15h 32m 08.2s 
   Dec(J2000) = -53d 18' 50.6" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.
 
The BAT light curve showed a complex structure with a duration of about 32 sec.
T90 (15-350 keV) is 17.79 +- 2.77 sec (estimated error including systematics).
 
The time-averaged spectrum from T+1.01 to T+20.94 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.83 +- 0.20.  The fluence in the 15-150 keV band is 3.9 +- 0.5 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+11.58 sec in the 15-150 keV band
is 0.6 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1340954