GCN Circular 3637

J. Cummings (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC),
E. Fenimore (LANL), N. Gehrels (GSFC), K. Gendreau (GSFC),
D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
P. Meszaros (PSU), T. Mitani (ISAS), D. Palmer (LANL), A. Parsons (GSFC), 
T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Suzuki (Saitama), J. Tueller (GSFC),
on behalf of the Swift/BAT team:

At 10:30:52.21 UT Swift-BAT detected GRB 050717 (trigger=146372)
(GCN Circ 3633, C. Hurkett et al.).  The refined BAT ground position
is (RA,Dec) = 214.352, -50.541, [deg; J2000] +- 3 arcmin, (90%
containment).  The partial coding was 55%.  

The masked-weighted light curve shows a large peak (starting at T+2.4 sec
and reaching a maximum at T+2.8 sec), followed by an exponential decay
with several smaller peaks.  There are two much smaller precursor peaks
at T+0 and T+0.7 sec, each with a 15-350 keV fluence of ~7 x 10^-8 erg/cm2.
BAT triggered on the first these two precursor peaks.  T90 (15-350 keV) is
(86 +- 2) sec (estimated error including systematics).  

The power-law photon index of the time-averaged spectrum is 1.42 +- 0.05.  
The fluence in the 15-350 keV band is (1.27 +- 0.05) x 10^-5 erg/cm2.  
The 1-sec peak photon flux measured from T+2.8 sec in the 15-350 
band is (8.5 +- 0.4) ph/cm2/sec.  All the quoted errors are at the 90% 
confidence level.