GCN Circular 6551

G. Sato (GSFC/ISAS) and S. Barthelmy (GSFC)
on behalf of the Swift-BAT team:

The time-averaged spectrum from T-2.6 to T+602.2 sec is best fit
by a simple power-law model.  The power law index of the time-averaged
spectrum is 1.61 +- 0.04.  The fluence in the 15-150 keV band is
1.92 +- 0.03 x 10^-5 erg/cm2.  The 1-sec peak photon flux measured
from T+139.74 sec in the 15-150 keV band is 1.9 +- 0.1 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.
 
The mask-weighted light curve shows many peaks.  The burst started with 
a low-level smooth emission at ~T-55 sec continuing smoothly and increasing
slowly until ~T+100 sec when the main emission started.  The main peak is
at T+120 sec.  Smaller overlapping peaks continue out past T+550 sec.
In particular, there is a small peak from T+730 to T+850 sec which is coincident
with a peak (flare) in the XRT lightcurve (Fig 2, GCN Report 66.1,
Starling et al.).  T90 (15-350 keV) is 402 +- 10 sec (estimated error
including systematics).