TITLE:   GCN CIRCULAR
NUMBER:  18959
SUBJECT: GRB 160131A: Swift-BAT refined analysis
DATE:    16/01/31 19:00:27 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), 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 downlinks,
we report further analysis of BAT GRB 160131A (trigger #672236)
(Page, et al., GCN Circ. 18951).  The BAT ground-calculated position is
RA, Dec = 78.170, -7.037 deg, which is 
   RA(J2000)  =  05h 12m 40.8s 
   Dec(J2000) = -07d 02' 13.0" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 64%.
 
The mask-weighted light curves shows a small precursor starting at ~T-2 sec
and the main peak is a FRED starting at ~T+10 sec, peaking at ~T+18 sec, and returning
to baseline at ~T+800 sec (although there is a possibility that it goes longer
but the observing window ended at T+950 sec).
T90 (15-350 keV) is 325 +- 72 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.49 to T+773.03 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.24 +- 0.05.  The fluence in the 15-150 keV band is 2.04 +- 0.05 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+15.97 sec in the 15-150 keV band
is 6.4 +- 0.3 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/672236/BA/