[vsnet-grb-info 14305] Konus-Wind observation of GRB 131226A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15619
SUBJECT: Konus-Wind observation of GRB 131226A
DATE:    13/12/27 14:44:44 GMT
FROM:    Valentin Pal'shin at Ioffe Inst  <val at mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long-duration GRB 131226A (Swift-BAT trigger 582123: Oates, et al., 
GCN 15612; Stamatikos, et al. GCN 15613) triggered Konus-Wind at 
T0=20858.013 s UT (05:47:38.013).

The burst light curve shows a multi-peaked structure with a total 
duration of ~7 s.

As observed by Konus-Wind, the burst
had a fluence of 1.01(-0.07,+0.08)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+2.704 s,
of (5.0 +/- 1.0)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+8.448 s)
is well fitted (in the 20 keV - 2 MeV range) by a power law with 
exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with
alpha = -0.90(-0.12,+0.13),  and
Ep = 264(-17,+20) keV (chi2 = 65.6/60 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and only an upper limit on the high energy
photon index: beta < -2.5.

All the quoted values are preliminary.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB131226_T20858/