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GCN Circular 32872

Subject
Konus-Wind detection of GRB 221017A
Date
2022-10-28T12:04:43Z (2 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A.Ridnaia, D. Frederiks, A.Lysenko, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 221017A
(MAXI/GSC detection: Nawa et al., GCN 32777;
IPN triangulation: Kozyrev et al., GCN 32787;
CALET/CGBM detection: Cherry et al., GCN 32813)
triggered Konus-Wind at T0=19789.594 s UT (05:29:49.594).

The burst light curve shows a multipeaked structure
which starts at ~T0-19.1 s and has a total duration of ~332 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/GRB221017_T19789/

As observed by Konus-Wind, the burst
had a fluence of 3.90(-0.32,+0.32)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+175.872 s,
of 9.62(-1.55,+1.56)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+312.320 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 = -0.99(-0.06,+0.07),
the high energy photon index beta = -2.75(-0.46,+0.23),
the peak energy Ep = 237(-15,+16) keV
(chi2 = 119/98 dof).

The spectrum near the maximum count rate
(measured from T0+151.552 to T0+182.016 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 = -0.92(-0.04,+0.04),
the high energy photon index beta = -2.98(-0.35,+0.22),
the peak energy Ep = 288(-13,+13) keV
(chi2 = 137/98 dof).

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