GCN Circular 13949
Subject
GRB 121031A, Early peak observed with Swift-BAT
Date
2012-11-03T02:06:03Z (11 years ago)
From
Jay R. Cummings at NASA/GSFC/Swift <james.r.cummings@nasa.gov>
GRB 121031A, Early peak observed with Swift-BAT
J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
With an additional data set from T-240 to T-61 sec, we report further
analysis of BAT GRB 121031 (trigger #537195) (D'Elia, et al., GCN Circ.
13934). In an earlier circular (Barthelmy, et al., GCN Circ. 13936) we
described the second of two equal-sized peaks from this burst. BAT
triggered on that second peak. The earlier peak occurred during a pre-
planned slew maneuver, and its time interval was not covered by the data
available at the time the circular was produced.
The entire burst had two large peaks at T-190 and T0 that were about the
same in flux, duration, and shape. Each was a FRED about 60 seconds long as
seen in BAT. There was a small peak at T-50 sec of about 5 seconds duration.
For the entire burst, T90 (15-350 keV) was 226 +- 19 sec (estimated error
including systematics).
The time-averaged spectrum from T-209.0 to T+98.3 sec is best fit by a
simple power-law model. The power law index of the time-averaged spectrum
is 1.50 +- 0.05. The fluence in the 15-150 keV band is
7.8 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from
T-190.72 sec in the 15-150 keV band is 2.4 +- 0.2 ph/cm2/sec. All the
quoted errors are at the 90% confidence level.