TITLE:   GCN CIRCULAR
NUMBER:  15499
SUBJECT: GRB 131117A, Swift-BAT refined analysis
DATE:    13/11/17 20:11:55 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (NASA/UMBC),
C. B. Markwardt (GSFC), M. J. Page (UCL-MSSL) D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 131117A (trigger #577968)
(Page, et al., GCN Circ. 15490).  The BAT ground-calculated position is
RA, Dec = 332.354, -31.761 deg which is
  RA(J2000)  =  22h 09m 25.0s
  Dec(J2000) = -31d 45' 38.8"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.

The mask-weighted light curve shows a single peak structure starts at ~T-1 sec
and ends at ~T+12 sec. T90 (15-350 keV) is 11.00 +- 3.16 sec (estimated error
including systematics).

The time-averaged spectrum from T-1.00 to T+12.00 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.40 +- 1.41,
and Epeak of 44.0 +- 7.4 keV (chi squared 45.16 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 2.5 +- 0.4 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+0.00 sec in the 15-150 keV band is
0.7 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.79 +- 0.18 (chi squared 58.98 for 57 d.o.f.).  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/577968/BA/