TITLE:   GCN CIRCULAR
NUMBER:  15354
SUBJECT: GRB 131018A, Swift-BAT refined analysis
DATE:    13/10/18 23:08:41 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. N. Ukwatta (MSU), 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), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC),
A. Melandri (INAF-OAB), D. M. Palmer (LANL), 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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 131018A (trigger #574935)
(Melandri, et al., GCN Circ. 15349).  The BAT ground-calculated position is
RA, Dec = 98.473, -19.897 deg which is
  RA(J2000)  =  06h 33m 53.4s
  Dec(J2000) = -19d 53' 48.5"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single long peak starts at ~T+21 sec
and ends at ~T+118 sec. T90 (15-350 keV) is 73.22 +- 18.97 sec
(estimated error including systematics).

The time-averaged spectrum from T+21.10 to T+117.74 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.24 +- 0.14.  The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+59.41 sec in the 15-150 keV band
is 0.5 +- 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/574935/BA/