[vsnet-grb-info 16062] Konus-Wind observation of GRB 150118B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17344
SUBJECT: Konus-Wind observation of GRB 150118B
DATE:    15/01/22 11:30:17 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The long-duration, hard-spectrum, intense GRB 150118B
(Fermi-LAT detection: Kocevski et al., GCN 17307;
Fermi-GBM detection: Stanbro, GCN 17308;
IPN triangulation: Hurley et al., GCN 17342)
triggered Konus-Wind at T0=35302.394 s UT (09:48:22.394).

The light curve shows multiple emission episodes from ~T0-8 s to ~T0+60 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150118_T35302/

As observed by Konus-Wind, the burst had a fluence
of 1.87(-0.15,+0.14)x10^-4 erg/cm2, and a 64-ms peak flux,
measured from T0+39.680 s, of 1.88(-0.18,+0.20)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+58.368 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -0.98(-0.04,+0.04),
and the peak energy Ep = 695(-42,+47) keV,
chi2 = 103/97 dof.
Fitting this spectrum with the Band model yields the same
values of alpha and Ep with an upper limit on beta of -2.8

The spectrum near the peak count rate (measured from T0+35.328 to T0+41.984 s)
is best fit in the 20 keV - 15 MeV range
by the cutoff power law with the following model parameters:
the photon index alpha = -0.84(-0.08,+0.08),
and the peak energy Ep = 614(-55,+64) keV,
chi2 = 115/98 dof.

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