[vsnet-grb-info 8222] GRB 090807, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9749
SUBJECT: GRB 090807, Swift-BAT refined analysis
DATE:    09/08/07 20:06:11 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.krimm at nasa.gov>

T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. K. Cannizzo (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+423 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 090807 (trigger #359378)
(Cannizzo, et al., GCN Circ. 9746).  The BAT ground-calculated position is
RA, Dec = 273.741, 10.279 deg which is
   RA(J2000)  =  18h 14m 57.8s
   Dec(J2000) = +10d 16' 45.9"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 64%.

The mask-weighted light curve shows a complex structure lasting from
T-5 to T+150 seconds with at least five peaks superimposed on a broad,
soft and slowly varying background.  There is an additional peak at
T+185 sec which corresponds to a large flare seen in the Swift/XRT.
There is also possible precursor activity from T-200 to T-80 sec.
T90 (15-350 keV) is 140.8 +- 13.1 sec (estimated error including
systematics).

The time-averaged spectrum from T-9.5 to T+151.5 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.25 +- 0.14.  The fluence in the 15-150 keV band is 2.2 +- 0.2 x 10-6 erg/cm2.
The 1-sec peak photon flux measured from T+41.96 sec in the 15-150 keV band
is 0.7 +- 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/359378/BA/