TITLE:   GCN CIRCULAR
NUMBER:  18837
SUBJECT: Konus-Wind observation of GRB 151225A
DATE:    16/01/07 12:36:03 GMT
FROM:    Anastasia Tsvetkova at Ioffe Institute  <tsvetkova@mail.ioffe.ru>

S. Golenetskii, R.Aptekar, D. Frederiks, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration, intense GRB 151225A
(CALET detection: Kawakubo et al., GCN 18724;
IPN triangulation: Golenetskii et al., GCN 18836)
triggered Konus-Wind at T0=68946.508 s UT (19:09:06.508).

The burst light curve shows a  multipeaked structure
with a total duration of ~1.1 s.
The emission is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 3.17(-0.85,+1.79)x10^-6 erg/cm2,
and a 16-ms peak energy flux, measured from T0+0.416 s,
of 2.22(-0.79,+1.46)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit 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 = -1.13(-0.48,+0.74),
and Ep = 360(-153,+741) keV (chi2 = 56/62 dof).
Fitting by the GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index:
beta < -1.7 (chi2 = 56/61 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB151225_T68946/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.