[vsnet-grb-info 9547] GRB 100728A, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11018
SUBJECT: GRB 100728A, Swift-BAT refined analysis 
DATE:    10/07/28 15:22:22 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.a.krimm at nasa.gov>

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

Using the data set from T-130 to T+963 sec from the recent telemetry 
downlink,
we report further analysis of BAT GRB 100728A (trigger #430151)
(Cannizzo, et al., GCN Circ. 11004).  The BAT ground-calculated position is
RA, Dec = 88.753, -15.259 deg which is
  RA(J2000)  =  05h 55m 00.7s
  Dec(J2000) = -15d 15' 33.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 81%.

The BAT light curve is quite complex with a long series of peaks and flares
extending from approximately T-100 sec to T+750 sec.  Detected emission
began around T-100 sec, rising to a first peak at T-40 sec.  The burst
continued as a series of at least ten overlapping peaks with the strongest
peak centered at T+30 sec.  There was a strong set of BAT peaks centered
at T+120 sec, corresponding with the second flare detected by the XRT
(Evans & Cannizzo, GCN Circ 11014).  This was followed by a series of 
weaker
flares out to T+750 sec, at times which appear to correspond to flares
detected by the XRT. The burst triggered just after the spacecraft settled
following a slew to a pre-planned target, so it is possible that there was
some very early emission (before T-120 sec) which was not detected. T90
(15-350 keV) is 198.5 +- 12.7 sec (estimated error including systematics).

The time-averaged spectrum from T-84.3 to T+334.0 sec is best fit by a
simple power-law model.  The power law index of the time-averaged spectrum
is 1.18 +- 0.02.  The fluence in the 15-150 keV band is 3.8 +- 0.0 x 10^-5
erg/cm2. The 1-sec peak photon flux measured from T+28.26 sec in the 15-150
keV band is 5.1 +- 0.2 ph/cm^2/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/430151/BA/