[vsnet-grb-info 20248] Konus-Wind observation of GRB 180113A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22344
SUBJECT: Konus-Wind observation of GRB 180113A
DATE:    18/01/15 15:37:30 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 180113A (Swift/BAT detection: Ukwatta et al.,
GCN 22325, GCN 22332; Fermi-GBM detection: Veres, GCN 22328)
triggered Konus-Wind at T0=10027.005 s UT (02:47:07.005).

The KW light curve shows a single pulse with a total duration
of ~13 s. The emission is seen up to ~1 MeV.

As observed by Konus-Wind, the burst had a fluence of
(1.36 ± 0.10)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+0.448, of (3.1 ± 0.3)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+16.640 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 = -0.80(-0.12,+0.13),
and the peak energy Ep = 293(-29,+36) keV,
chi2 = 72/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of ~-3.0.

The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by
the CPL function with the following model parameters:
the photon index alpha = -0.72(-0.12,+0.13),
and the peak energy Ep = 308(-30,+36) keV,
chi2 = 83/98 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep, and an upper limit on beta of ~-3.0.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180113_T10027/

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