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GCN Circular 31022

Subject
Konus-Wind detection of GRB 211023A
Date
2021-10-28T21:24:26Z (3 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 211023A (Fermi-GBM detection:
Fermi GBM Team, GCN 30958; Lesage et al., GCN 30965;
Fermi-LAT detection: Di Lalla et al., GCN 30961;
AGILE detection: Ursi et al., GCN 30969)
triggered Konus-Wind at T0=47199.142 s UT (13:06:39.142).

The burst light curve shows a multipeaked structure
started at ~T0-65.3 s with a total duration of ~207.9 s.
The emission is seen up to ~6 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB211023_T47199/

As observed by Konus-Wind, the burst
had a fluence of 1.13(-0.04,+0.05)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+6.368 s,
of 5.12(-1.01,+1.01)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+103.936 s)
is best fit in the 20 keV - 6 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.85(-0.03,+0.03)
and Ep = 122(-12,+15) keV (chi2 = 100/79 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 99/78).

The spectrum near the maximum count rate
(measured from T0+5.888 to T0+10.496 s)
is best fit in the 20 keV - 6 MeV range
by a power law with exponential cutoff model
with  alpha = -1.27(-0.06,+0.06)
and Ep = 267(-22,+27) keV (chi2 = 76/72 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 = 75/71).

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