TITLE:   GCN CIRCULAR
NUMBER:  28398
SUBJECT: GRB 200907B: Swift-BAT refined analysis
DATE:    20/09/08 22:17:25 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J. R. Cummings (CPI),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), 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-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 200907B (trigger #995004)
(Beardmore et al., GCN Circ. 28384).  The BAT ground-calculated position is
RA, Dec = 89.019, 6.905 deg which is
   RA(J2000)  =  05h 56m 04.5s
   Dec(J2000) = +06d 54' 17.7"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T-0.6 and ends at ~T+0.3 s. The main peak occurs
at ~T+0.1 s. T90 (15-350 keV) is 0.83 +- 0.13 sec (estimated error
including systematics).

The time-averaged spectrum from T-0.64 to T+0.28 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 0.68 +- 0.25.  The fluence in the 15-150 keV band
is 1.6 +- 0.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured
from T-0.68 sec in the 15-150 keV band is 1.5 +- 0.2 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/995004/BA/