TITLE:   GCN CIRCULAR
NUMBER:  18268
SUBJECT: GRB 150910A: Swift-BAT refined analysis
DATE:    15/09/10 13:19:46 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
C. Pagani (U Leicester), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from the recent telemetry downlinks,
we report further analysis of BAT GRB 150910A (trigger #655097)
(Pagani, et al., GCN Circ. 18264).  The BAT ground-calculated position is
RA, Dec = 5.677, 33.466 deg, which is 
   RA(J2000)  =  00h 22m 42.5s 
   Dec(J2000) = +33d 27' 56.8" 
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 14%.
 
The mask-weighted light curve shows the burst definitely starting at ~T-150 sec
(and posibly before T-240 when we start having data), peaking at ~T+83 sec,
and ending at ~T+450 sec.  T90 (15-350 keV) is 112.2 +- 38.3 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-5.00 to T+149.75 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.42 +- 0.12.  The fluence in the 15-150 keV band is 4.8 +- 0.4 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+82.89 sec in the 15-150 keV band
is 1.1 +- 0.4 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/655097/BA/