TITLE:   GCN CIRCULAR
NUMBER:  16756
SUBJECT: GRB 140828A, Swift-BAT refined analysis
DATE:    14/08/29 22:54:54 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto@phys.aoyama.ac.jp>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 140828A (trigger #610953)
(Melandri, et al., GCN Circ. 16751).  The BAT ground-calculated position is
RA, Dec = 142.029, 14.569 deg which is 
  RA(J2000)  =  09h 28m 07.0s 
  Dec(J2000) = +14d 34' 09.2" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 26%.

The mask-weighted light curve shows a single peak starting at T-7 sec, peaking 
at T+1 sec and ending at T+10 sec.  There is a hint of an emission peaking 
at T+14 sec.  T90 (15-350 keV) is 18.8 +- 4.0 sec (estimated error including 
systematics).

The time-averaged spectrum from T-5.8 to T+18.4 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.6 +- 0.7, 
and Epeak of 54 +- 11 keV (chi squared 70.26 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+0.51 sec in the 15-150 keV band is
2.2 +- 0.3 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.78 +- 0.13 (chi squared 81.57 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/610953/BA/