[AAVSO-HEN] GRB 070917, Swift-BAT refined analysis

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  6792
SUBJECT: GRB 070917, Swift-BAT refined analysis
DATE:    07/09/17 14:34:18 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-120 to T+129 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 070917 (trigger #291292)
(Cummings, et al., GCN Circ. 6791).  The BAT ground-calculated position is
RA, Dec = 293.923, 2.420 deg which is 
   RA(J2000)  = 19h 35m 41.5s 
   Dec(J2000) = 02d 25' 12" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 79%.
 
The mask-weighted lightcurve starts at ~T-5 sec, has a sharp rise from
T-0.1 sec to ~T+0.3 sec, peaks at ~T+0.4 sec, and then approximately
exponentially decays to background at ~T+30 sec.
T90 (15-350 keV) is 7.3 +- 0.2 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.1 to T+11.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.52 +- 0.05.  The fluence in the 15-150 keV band is 2.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.21 sec in the 15-150 keV band
is 8.5 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.