GCN Circular 25973
Subject
Konus-Wind observation of GRB 191004A
Event
Date
2019-10-07T17:53:55Z (6 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@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 191004A
(Swift-BAT detection: Cenko et al., GCN circ. 25945;
Sakamoto et al., GCN circ. 25953)
triggered Konus-Wind at T0=65226.378 s UT (18:07:06.378).
The burst light curve shows a multi-peaked structure
which starts at ~T0-0.2 s and has a total duration of ~5 s.
The emission is seen up to ~1 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB191004_T65226/
As observed by Konus-Wind, the burst
had a fluence of 2.00(-0.41,+0.62)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+1.872 s,
of 2.38(-0.83,+1.02)x10^-6 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 a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.69(-0.61,+0.83)
and Ep = 157(-37,+95) keV (chi2 = 49/57 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.0
(chi2 = 48/56 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.