[vsnet-grb-info 23990] Konus-Wind observation of GRB 191025B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26089
SUBJECT: Konus-Wind observation of GRB 191025B
DATE:    19/10/29 12:34:07 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

A. Ridnaia, 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 191025B
(Insight-HXMT detection: Luo et al., GCN Circ. 26081;
IPN triangulation: Svinkin et al., GCN Circ. 26086)
triggered Konus-Wind at T0=67331.034 s UT (18:42:11.034).

The burst light curve shows a single pulse
started at ~T0 with a total duration of ~0.2 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 8.41(-1.44,+1.52)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0-0.006 s,
of 1.32(-0.32,+0.33)x10^-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.84(-0.11,+0.13)
and Ep = 2184(-608,+812) keV (chi2 = 23/26 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -1.9
(chi2 =22/25 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB191025_T67331/

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