TITLE:   GCN CIRCULAR
NUMBER:  11289
SUBJECT: GRB 100917A: Swift-BAT refined analysis
DATE:    10/09/17 18:46:15 GMT
FROM:    Craig Markwardt at NASA/GSFC/UMD  <craigm@milkyway.gsfc.nasa.gov>

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

Using the data set from T-240 to T+960 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 100917A (trigger
#434360) (Littlejohns, et al., GCN Circ. 11288).  The BAT ground-
calculated position is RA, Dec = 289.250, -17.120 deg which is
    RA(J2000)  =  19h 17m 00.1s
    Dec(J2000) = -17d 07' 12.1"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 62%.

The mask-weighted light curve shows a FRED-like profile with rise time
of ~5 sec and decay time of ~30 sec.  T90 (15-350 keV) is 66 +- 22 sec
(estimated error including systematics).

The time-averaged spectrum from T-2.1 to T+76 sec is best fit by a
simple power-law model.  The power law index of the time-averaged
spectrum is 1.67 +- 0.23.  The fluence in the 15-150 keV band is 8.6 +-
1.2 x 10^-7 erg/cm2.  The 1-sec peak photon flux measured from T+3.22
sec in the 15-150 keV band is 0.6 +- 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/434360/BA/