TITLE:   GCN CIRCULAR
NUMBER:  18636
SUBJECT: Konus-Wind observation of GRB 151120A
DATE:    15/11/23 10:14:13 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova@mail.ioffe.ru>

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

The long-duration GRB 151120A
(INTEGRAL ISGRI detection: S. Mereghetti et al., GCN Circ. 18623;
Fermi GBM detection: A. von Kienlin, GCN Circ. 18628)
triggered Konus-Wind at T0=30171.357 s UT (08:22:51.357).

The burst light curve shows a multipeaked structure
started at ~T0-1.3 s with a total duration of ~20 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB151120_T30171/

As observed by Konus-Wind, the burst
had a fluence of 7.20(-1.25,+1.79)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.752 s,
of 2.09(-0.88,+1.15)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+24.832 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.26 (-0.48,+0.77),
the high energy photon index beta = -2.70 (-0.88,+0.35),
the peak energy 106 (-19,+20) keV
(chi2 = 84/85 dof)

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = 0.81 (-0.75,+3.91),
the high energy photon index beta = -2.42 (-0.38,+0.35),
the peak energy 113 (-40,+22) keV
(chi2 = 81/82 dof)

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