TITLE:   GCN CIRCULAR
NUMBER:  15370
SUBJECT: GRB 131024A, Swift-BAT refined analysis
DATE:    13/10/24 20:47:07 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), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 131024A (trigger #575707)
(Racusin, et al., GCN Circ. 15365).  The BAT ground-calculated position is
RA, Dec = 290.544, -64.599 deg which is
    RA(J2000)  =  19h 22m 10.5s
    Dec(J2000) = -64d 35' 54.8"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%. The burst started during a pre-planned slew. 
Low-level emission begins around T-150 sec. Then there is a first peak from T-70 
to T-50 sec, a second peak from T-15 to T-4 sec and a third peak from T-2 to 
T+20 sec.  We note that there is a gap in the currently available data from 
~T-140 to T-120 sec. T90 (15-350 keV) is 112.00 +- 36 sec (estimated error 
including systematics).

The time-averaged spectrum from T-111.00 to T+17.00 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.85 +- 0.18.  The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-55.50 sec in the 15-150 keV band
is 0.3 +- 0.1 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/575707/BA/