[vsnet-grb-info 20259] Konus-Wind observation of GRB 180113B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22355
SUBJECT: Konus-Wind observation of GRB 180113B
DATE:    18/01/16 15:18:46 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

D. Frederiks, S. Golenetskii, R.Aptekar, 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 GRB 180113B (Fermi-GBM detection: Veres & Meegan, GCN 22329;
Insight-HXMT/HE observation: Li et al., GCN 22342;
IPN Triangulation: Svinkin et al., GCN 22354)
triggered Konus-Wind at T0=958.621 s UT (00:15:58.621).

The KW light curve shows a multiple pulses in the interval
from ~T0 to ~T0+20 s. The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst had a fluence of
(4.05 ± 0.29)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+3.200 s, of (2.2 ± 0.1)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+20.224 s)
is best fit in the 20 keV - 15 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -0.97(-0.07,+0.08),
and the peak energy Ep = 559(-58,+71) keV,
chi2 = 81/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of ~-2.0.

The spectrum near the peak count rate (measured from T0 to T0+3.840 s)
is best fit in the 20 keV - 15 MeV range by
the CPL function with the following model parameters:
the photon index alpha = -0.80(-0.06,+0.06),
and the peak energy Ep = 611(-47,+53) keV,
chi2 = 93/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of ~-2.0.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180113_T00958/

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.