TITLE:   GCN CIRCULAR
NUMBER:  10180
SUBJECT: GRB 091117 BAT refined analysis
DATE:    09/11/19 19:18:16 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <james.r.cummings@nasa.gov>

T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (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),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-0.16 to T+10 sec, we report further analysis
of BAT/IPN GRB 091117 (trigger #376211) (Cummings, et al.,
GCN Circ.# 10171).  The BAT ground-calculated position is as reported
before, RA, Dec = 30.945, -16.944, which is
RA (J2000) 02h 03m 46.9s
Dec (J2000) -16d 56' 38.0"
with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 12%.
 
The mask-weighted light curve shows two peaks. The first is a weak spike
at T+0 lasting for 0.15 sec. The second is the main spike at T+2.7
lasting for 0.4 sec.  T90 (15-350 keV) is 0.43 +- 0.05 sec (estimated
error including systematics).  There is an indication of possible
extended-time soft emission in the mask-weighted image covering ~1 minute
in the 15-50 keV band following the burst (2.6 sigma).  There is no
indication of a persistent source in the BAT energy band at this position
at other times.
 
The time-averaged spectrum from T-2.5 to T+3.2 sec is best fit by a
simple power-law model.  The power law index of the time-averaged
spectrum is 0.8 +- 0.3.  The fluence in the 15-150 keV band is
3.5 +- 1.2 x 10-7 erg/cm2**.  The 1-sec peak photon flux measured from
T+2.3 sec in the 15-150 keV band is 2.5 +- 0.5 ph/cm2/sec.  All the
quoted errors are at the 90% confidence level.

Because of the ground-detected nature of this burst, the usual automated
data products are not currently available.