[vsnet-grb-info 14306] GRB 131227A: Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15620
SUBJECT: GRB 131227A: Swift-BAT refined analysis
DATE:    13/12/27 15:00:28 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.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 (NASA/UMBC),
C. B. Markwardt (GSFC), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+651 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 131227A (trigger #582184)
(Oates, et al., GCN Circ. 15616).  The BAT ground-calculated position is
RA, Dec = 67.369, 28.879 deg which is 
   RA(J2000)  =  04h 29m 28.5s 
   Dec(J2000) = +28d 52' 44.3" 
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 90%.
 
The mask-weighted light curve shows several overlapping peaks starting
at ~T-2 sec, peaking at ~T+2 sec, and ending at ~T+22 sec with a long low-level
tail out to ~T+100 sec.  T90 (15-350 keV) is 18.0 +- 1.6 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-1.19 to T+19.23 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.36 +- 0.12.  The fluence in the 15-150 keV band is 8.4 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+1.61 sec in the 15-150 keV band
is 1.1 +- 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/582184/BA/