GCN Circular 12160

T. N. Ukwatta (MSU) S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
E. Sonbas (GSFC/USRA/Adiyaman Univ.), M. Stamatikos (OSU), J. Tueller (GSFC),
(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 110715A (trigger #457330)
(Sonbas, et al., GCN Circ. 12158
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 237.665, -46.237 deg, which is 
   RA(J2000)  =  15h 50m 39.7s 
   Dec(J2000) = -46d 14' 13.9" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 69%.
 
The mask-weighted light curve shows a bright first peak, which is composed
of at least 2 overlapping peaks (at the lower energies), starting at ~T-10 sec
and peaking at ~T+2.5 sec.  the first peak never returns to basline before
the second and much weaker peak goes from ~T+12 to T+17 sec.
T90 (15-350 keV) is 13.0 +- 4.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-3.1 to T+20.9 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.25 +- 0.12, 
and Epeak of 120 +- 21 keV (chi squared 49.6 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.18 +- 0.02 x 10^-5 erg/cm2
and the 1-sec peak flux measured from T+1.86 sec in the 15-150 keV band is
53.9 +- 1.1 ph/cm2/sec.  To within the calibration limits, the Band model
fits equally well.  A fit to a simple power law gives a photon index
of 1.63 +- 0.03 (chi squared 81.5 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/457330/BA/