[vsnet-grb-info 26204] Konus-Wind detection of GRB 200826B

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28304
SUBJECT: Konus-Wind detection of GRB 200826B
DATE:    20/08/28 20:46:49 GMT
FROM:    Anna Ridnaia at Ioffe Institute  <ridnaia 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 long-duration, very bright GRB 200826B
(Fermi-GBM detection: The Fermi GBM Team, GCN Circ. 28292;
Malacaria & Meegan, GCN Circ. 28298;
IPN triangulation: Hurley et al., GCN Circ. 28303)
triggered Konus-Wind at T0=79779.087 s UT (22:09:39.087).

The burst light curve shows a bright, multi-peaked pulse
which started at ~T0-3 s and had a total duration of ~23 s.
A weak post-burst emission is visible in the 18-70 keV band
up to the end of the KW trigger record at ~T0+250 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/GRB200826_T79779/

As observed by Konus-Wind, the burst had
a fluence of (2.0 ± 0.1)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+4.922,
of (4.8 ± 0.4)x10^-5 erg/cm^2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+17.408 s)
can be described, in the 20 keV - 15 MeV range,
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.54 (-0.04,+0.04),
the high energy photon index beta = -2.38 (-0.07,+0.06),
the peak energy Ep = 337 (-14,+15) keV,
chi2 = 169/96 dof.

The spectrum near the peak count rate
(measured from T0+4.864 to T0+5.120 s)
is best fit in the 20 keV - 15 MeV range by the GRB (Band)
function with the following model parameters:
the low-energy photon index alpha = -0.18 (-0.18,+0.22),
the high energy photon index beta = -2.42 (-0.23,+0.17),
the peak energy Ep = 320 (-45,+48) keV,
chi2 = 58/48 dof.

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