TITLE:   GCN CIRCULAR
NUMBER:  11233
SUBJECT: GRB 100906A: Swift-BAT refined analysis
DATE:    10/09/06 16:31:20 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 100906A (trigger #433509)
(Markwardt, et al., GCN Circ. 11227).  The BAT ground-calculated position is
RA, Dec = 28.697, 55.634 deg, which is 
   RA(J2000)  =  01h 54m 47.4s 
   Dec(J2000) = +55d 38' 03.7" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 46%.
 
The mask-weighted light curve shows several bright peaks.  The first pair
of overlapping peaks starts at ~T-0.2 sec, peaks at ~T+2 and ~T+10 sec,
and almost returns to background at ~T+35 sec.  There is a small peak
at ~T+50 sec. Then there are four overlapping peaks from ~T+100 to ~T+118 sec.
T90 (15-350 keV) is 114.4 +- 1.6 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.2 to T+130.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.78 +- 0.03.  The fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+10.48 sec in the 15-150 keV band
is 10.1 +- 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/433509/BA/