[vsnet-grb-info 14193] Konus-Wind observation of GRB 13118A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  15507
SUBJECT: Konus-Wind observation of GRB 13118A
DATE:    13/11/21 08:06:58 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, and T. Cline on behalf
of the Konus-Wind team, report:

The long-duration GRB 131118A
(Fermi GBM detection: Collazzi, GCN 15503;
IPN triangulation: Hurley at al., GCN 15506)
triggered Konus-Wind at T0=82738.919 s UT (22:58:58.919).

The burst light curve shows multiple partly overlapped pulses
from ~T0 to ~T0+140 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/GRB131118_T82738/
Note: the waiting mode LCs are corrupted for almost whole
duration of the burst.

As observed by Konus-Wind, the burst
had a fluence of (8.40 ± 0.06)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+63.296 s,
of (5.1 ± 0.5)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+139.520 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.88 ± 0.05,
the high energy photon index beta = -2.83 ± 0.25,
the peak energy Ep = 230 ± 11 keV,
chi2 = 97.4/96 dof.

The spectrum near the maximum count rate
(measured from T0+57.600 s to T0+65.792 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.80 ± 0.04,
the high energy photon index beta = -2.56 ± 0.07,
the peak energy Ep = 286 ± 8 keV,
chi2 = 110/97 dof.

All the quoted values are preliminary.