[vsnet-grb-info 15556] GRB 140927A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16845
SUBJECT: GRB 140927A: Swift-BAT refined analysis
DATE:    14/09/27 21:49:44 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), R. L. C. Starling (U Leicester)
J. Tueller (GSFC), 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 140927A (trigger #613775)
(Starling, et al., GCN Circ. 16842).  The BAT ground-calculated position is
RA, Dec = 291.802, -65.400 deg which is
  RA(J2000)  =  19h 27m 12.5s
  Dec(J2000) = -65d 23' 58.4"
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 54%.

The mask-weighted light curve shows a multi-peaked structure starts at ~ T0 and
ends at ~ T+9 s. The structure has roughly two main peaks, at ~ T+3.8 s and ~ T+7.7 s,
respectively. T90 (15-350 keV) is 6.26 +- 1.43 sec (estimated error including systematics).

The time-averaged spectrum from T+0.43 to T+8.70 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.82 +- 0.30.  The fluence in the 15-150 keV band is 2.7 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+7.70 sec in the 15-150 keV band
is 0.9 +- 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/613775/BA/