[vsnet-grb-info 24027] Konus-Wind observation of GRB 191031D

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26126
SUBJECT: Konus-Wind observation of GRB 191031D
DATE:    19/11/01 11:56:53 GMT
FROM:    Dmitry Frederiks at Ioffe Institute  <fred at mail.ioffe.ru>

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

The short-duration GRB 191031D
(Swift detection: D'Elia et al., GCN Circ. 26112;
Fermi GBM detection: Mailyan & Meegan, GCN Circ. 26118;
AGILE/MCAL observations: Ursi et al., GCN Circ. 26123)
triggered Konus-Wind at T0=77011.324 s UT (21:23:31.324).

The burst light curve shows a mult-peaked pulse
which started at ~T0-0.064 s and had a total duration of ~0.35 s.
The emission is seen up to ~5 MeV.

As observed by Konus-Wind, the burst
had a fluence of 2.72(-0.27, +0.31)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0-0.016 s,
of 1.95(-0.32,+0.38)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.27(-0.17,+0.20)
and Ep = 370(-46,+58) keV (chi2 = 35/39 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 =35/38 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB191031_T77011/

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