[vsnet-grb-info 20528] Konus-Wind observation of GRB 180404C

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22624
SUBJECT: Konus-Wind observation of GRB 180404C
DATE:    18/04/10 14:05:04 GMT
FROM:    Dmitry Svinkin at Ioffe Institute  <svinkin at mail.ioffe.ru>

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

The long-duration GRB 180404C
(CATET-GBM detection: Marrocchesi et al., GCN Circ. 22607;
IPN triangulation: Hurley et al., GCN Circ. 22610)
triggered Konus-Wind at T0=78131.929 s UT (21:42:11.929).

The burst light curve shows a multi-peaked structure
which starts at ~T0-88 s and has a total duration of ~200 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/GRB180404_T78131/

As observed by Konus-Wind, the burst
had a fluence of 1.33(-0.18,+0.19)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+2.672 s,
of 2.11(-0.37,+0.37)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+116.736 s)
is best fit in the 20 keV - 19 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.00(-0.10,+0.12),
the high energy photon index beta = -2.40(-0.56,+0.24),
the peak energy Ep = 342(-49,+58) keV
(chi2 = 91/97 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+4.864 s)
is best fit in the 20 keV - 19 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.58(-0.11,+0.13),
the high energy photon index beta = -2.00(-0.12,+0.09),
the peak energy Ep = 517(-71,+86) keV
(chi2 = 86/94 dof).

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