TITLE:   GCN CIRCULAR
NUMBER:  13749
SUBJECT: GRB 120911A: Swift-BAT refined analysis
DATE:    12/09/11 13:18:13 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. K. Cannizzo (NASA/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+863 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120911A (trigger #533268)
(Cannizzo, et al., GCN Circ. 13744).  The BAT ground-calculated position is
RA, Dec = 357.966, 63.090 deg, which is 
   RA(J2000)  =  23h 51m 51.9s 
   Dec(J2000) = +63d 05' 25.6" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 23%.
 
The mask-weighted light curve shows two barely overlapping peaks starting
at ~T-4 sec, peaking at ~T+1 and ~T+17 sec, and ending at ~T+50 sec.
T90 (15-350 keV) is 17.8 +- 3.9 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.84 to T+24.10 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.71 +- 0.16.  The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.30 sec in the 15-150 keV band
is 2.7 +- 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/533268/BA/