TITLE:   GCN CIRCULAR
NUMBER:  26131
SUBJECT: GRB 191031A: Swift-BAT refined analysis
DATE:    19/11/01 19:05:44 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), 
A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), 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-61 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 191031A (trigger #932435)
(D'Ai, et al., GCN Circ. 26101).  The BAT ground-calculated position is
RA, Dec = 233.490, 6.109 deg which is 
 RA(J2000)  =  15h 33m 57.7s 
 Dec(J2000) = +06d 06' 32.9" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 46%.

The mask-weighted light curve shows a single pulse with some overlying 
structure.  The emission starts at ~T-8 sec, peaks at T+3 sec, and decays
to background by ~T+18 sec. A pre-planned spacecraft slew took the burst
location out of the field of view by T+95 sec. T90 (15-350 keV) is 19.1 +- 6.3 sec 
(estimated error including systematics).

The time-averaged spectrum from T-11.08 to T+16.87 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.38 +- 0.19.  The fluence in the 15-150 keV band is 9.0 +- 1.1 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+3.48 sec in the 15-150 keV band
is 1.0 +- 0.2 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/932435/BA/