[vsnet-grb-info 19758] Konus-Wind observation of GRB 170826B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21767
SUBJECT: Konus-Wind observation of GRB 170826B
DATE:    17/08/30 15:05:24 GMT
FROM:    Anna Kozlova at Ioffe Institute  <ann_kozlova at mail.ioffe.ru>

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

The long-duration GRB 170826B (Fermi GBM observation: Poolakkil
et al., GCN 21717; Insight-HXMT detection: Li et al., GCN 21739;
IPN Triangulation: Hurley et al., GCN 21753)
triggered Konus-Wind at T0=70742.555 s UT (19:39:02.555).

The burst light curve shows a multipeaked structure
which starts at ~T0-3.9 s and has a total duration of ~23.6 s.
The emission is seen up to ~10 MeV.

As observed by Konus-Wind, the burst
had a fluence of 5.70(-0.53,+0.53)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.728 s,
of 1.62(-0.29,+0.30)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+14.592 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.73(-0.14,+0.15),
the high energy photon index beta = -2.12(-0.14,+0.10),
the peak energy Ep = 261(-32,+46) keV
(chi2 = 87/83 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+6.400 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.54(-0.19,+0.20),
the high energy photon index beta = -2.05(-0.13,+0.09),
the peak energy Ep = 259(-36,+53) keV
(chi2 = 99/83 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170826_T70742/

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