[vsnet-grb-info 21357] Konus-Wind observation of GRB 181121A

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23456
SUBJECT: Konus-Wind observation of GRB 181121A
DATE:    18/11/26 14:55:41 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration GRB 181121A
(AGILE/MCAL detection: Ursi et al., GCN 23429;
AstroSat CZTI detection: Sharma et al., GCN 23447;
IPN Triangulation: Kozlova et al., GCN 23449)
triggered Konus-Wind at T0=74619.153 s UT (20:43:39.153).

The burst light curve shows a multipeaked structure
which starts at ~T0 s and has a total duration of ~1.4 s.
The emission is seen up to ~2 MeV.

As observed by Konus-Wind, the burst
had a fluence of 1.46(-0.26,+0.44)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.118 s,
of 9.44(-1.53,+1.77)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.83(-0.20,+0.46),
the high energy photon index beta = -2.58(-1.04,+0.46),
the peak energy Ep = 226(-65,+45) keV
(chi2 = 72/56 dof).

The spectrum near the maximum count rate
(measured from T0+0.064 to T0+0.192 s)
is best fit in the 20 keV - 2 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.27(-0.24,+0.32),
the high energy photon index beta = -2.54(-0.47,+0.28),
the peak energy Ep = 271(-47,+50) keV
(chi2 = 57/42 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB181121_T74619/

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