[vsnet-grb-info 14299] GRB 131226A, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15613
SUBJECT: GRB 131226A, Swift-BAT refined analysis
DATE:    13/12/26 13:30:30 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.a.krimm at nasa.gov>

M. Stamatikos (OSU), 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), J. Tueller (GSFC),
T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):

Using the data set from T-239 to T+481 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 131226A (trigger #582123)
(Oates, et al., GCN Circ. 15612).  The BAT ground-calculated position is
RA, Dec = 301.309, -64.943 deg which is
    RA(J2000)  =  20h 05m 14.2s
    Dec(J2000) = -64d 56' 35.2"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.

The mask-weighted light curve shows a very complex structure with more than a 
dozen peaks covering the time period from T-0.5 sec to T+8.5 sec and peaking at 
T+1 sec.  This is followed by lower-level extended emission out to ~T+180 sec. 
T90 (15-350 keV) is 7.20 +- 0.16 sec (estimated error including systematics).

The time-averaged spectrum from T-0.26 to T+8.42 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.38 +- 0.04.  The fluence in the 15-150 keV band is 4.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.11 sec in the 15-150 keV band
is 10.4 +- 0.4 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/582123/BA/