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GCN Circular 11486

Subject
GRB 101224A, Swift-BAT refined analysis
Date
2010-12-24T14:19:41Z (13 years ago)
From
Hans Krimm at NASA-GSFC <hans.a.krimm@nasa.gov>
C. B. Markwardt (GSFC), 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), 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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 101224A (trigger #440955)
(Krimm, et al., GCN Circ. 11484).  The BAT ground-calculated position is
RA, Dec = 285.939, 45.706 deg which is
     RA(J2000)  =  19h 03m 45.4s
     Dec(J2000) = +45d 42' 22.3"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.

The light curve consists of a pair of overlapping peaks of total
duration 0.2 sec, T90 (15-350 keV) is 0.2 +- 0.01 sec (estimated error
including systematics).

The time-averaged spectrum from T+0.0 to T+0.3 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.93 +- 1.52,
and Epeak of 95.7 +- 35.2 keV (chi squared 62.87 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 5.8 +- 1.1 x 10^-8 erg/cm2
and the 1-sec peak flux measured from T-0.34 sec in the 15-150 keV band is
0.7 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.05 +- 0.26 (chi squared 71.61 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The hardness ratio S(50-100 keV)/S(25-50 keV) is 1.94, which when plotted
against burst duration places GRB 101224A among the short-hard bursts in the
distribution.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/440955/BA/
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