TITLE:   GCN CIRCULAR
NUMBER:  11023
SUBJECT: GRB 100728B, Swift-BAT refined analysis 
DATE:    10/07/28 21:31:46 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. C. Morris (GWU/GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+350 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 100728B (trigger #430172)
(Morris, et al., GCN Circ. 11009).  The BAT ground-calculated position is
RA, Dec = 44.051, 0.296 deg which is
    RA(J2000)  =  02h 56m 12.2s
    Dec(J2000) = +00d 17' 45.9"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 11%.

The mask-weighted light curve shows a single peak of duration 10 seconds,
starting at T-2 sec and continuing at a low level to about T+20 sec. An
observing constraint moved the burst out of the BAT field of view at T+350
sec, but there is no sign of extended emission from this burst.
T90 (15-350 keV) is 12.1 +- 2.4 sec (estimated error including systematics).

The time-averaged spectrum from T-1.7 to T+13.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.55 +- 0.14.  The fluence in the 15-150 keV band is 1.7 +- 0.1 x 10-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.18 sec in the 15-150 keV band
is 3.5 +- 0.5 ph/cm2/sec.  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/430172/BA/