TITLE:   GCN CIRCULAR
NUMBER:  23306
SUBJECT: GRB 181003A: Swift-BAT refined analysis
DATE:    18/10/03 22:34:55 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

H. A. Krimm (NSF/USRA), S. D. Barthelmy (GSFC),
A. P. Beardmore, J. R. Cummings (CPI),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 181003A (trigger #865179)
(Beardmore et al., GCN Circ. 23295).  The BAT ground-calculated position is
RA, Dec = 52.481, -33.991 deg which is
  RA(J2000)  =  03h 29m 55.4s
  Dec(J2000) = -33d 59' 25.8"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a weak structure that starts at ~T-10 s
and ends at ~ T+20 s. The burst went out of the BAT field of view at ~T+97 s.
T90 (15-350 keV) is 21.5 +- 4.8 sec (estimated error including systematics).

The time-averaged spectrum from T-11.20 to T+18.01 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.20 +- 1.12,
and Epeak of 56.5 +- 14.4 keV (chi squared 52.40 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 4.2 +- 0.7 x 10^-7 erg/cm2
and the 1-sec peak flux measured from T+1.86 sec in the 15-150 keV band is
0.6 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.54 +- 0.19 (chi squared 63.13 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/865179/BA/