GCN Circular 14011

D. M. Palmer (LANL),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), S. R. Oates (UCL-MSSL),
T. Sakamoto (AGU), G. Sato (ISAS), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):

Using the data set from T-119 to T+195 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 121128A (trigger #539866)
(Oates, et al., GCN Circ. 14007
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 300.589, 54.301 deg which is
    RA(J2000)  =  20h 02m 21.3s
    Dec(J2000) = +54d 18' 02.6"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 88%.  The mask-weighted light curve shows a complex,
multi-peaked structure.  The burst began with a faint precursor at ~T-4 sec.
The main emission started at ~T+10 sec, peaked at T+22 sec and continued
until just after T+40 sec, with weak emission extending out to ~T+70 sec.
T90 (15-350 keV) is 23.3 +- 1.6 sec (estimated error including systematics).

The time-averaged spectrum from T-0.00 to T+41.69 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.32 +- 0.18,
and Epeak of 64.5 +- 6.8 keV (chi squared 33.43 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 6.9 +- 0.4 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+21.68 sec in the 15-150 keV band is
12.9 +- 0.4 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.86 +- 0.04 (chi squared 62.32 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/539866/BA/