[vsnet-grb-info 18513] GRB 160927A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19961
SUBJECT: GRB 160927A: Swift-BAT refined analysis
DATE:    16/09/28 07:13:26 GMT
FROM:    Takanori Sakamoto at AGU  <tsakamoto at phys.aoyama.ac.jp>

A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), S. L. Gibson (U Leicester), H. A. Krimm (GSFC/USRA),
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-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 160927A (trigger #713782)
(Gibson, et al., GCN Circ. 19952).  The BAT ground-calculated position is
RA, Dec = 256.268, 17.334 deg which is
    RA(J2000)  =  17h 05m 04.2s
    Dec(J2000) = +17d 20' 01.8"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 50%.
  
The mask-weighted light curve in 16 msec binning shows at least two
peaks.  The first peak starts at T-0.2 sec, peaks at T+0.2 sec and
ends at T+0.3 sec.  The second peak starts at T+0.3 sec, peaks at
T+0.4 sec and ends at T+0.5 sec.  T90 (15-350 keV) is 0.48 +- 0.10 sec
(estimated error including systematics).

The time-averaged spectrum from T+0 to T+0.54 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.12 +- 0.26.  The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.23 sec in the 15-150 keV band
is 1.9 +- 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/713782/BA/