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GCN Circular 31130

Subject
Konus-Wind detection of GRB 211120A
Date
2021-11-26T14:31:29Z (2 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 211120A (GECAM detection: Li et al., GCN 31100;
AstroSat CZTI detection: Prasad et al., GCN 31104;
AGILE detection: Ursi et al., GCN 31105;
IPN localization: Kozyrev et al., GCN 31129)
triggered Konus-Wind (KW) at T0=83120.396 s UT (23:05:20.396).

The burst light curve shows a bright, multi-peaked pulse
which starts at ~T0-1 s and has a total duration of ~8 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/GRB211120_T83120/

As observed by Konus-Wind, the burst had
a fluence of (3.5 �� 0.4)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 1.984 s,
of (2.4 �� 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 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 = -0.65 (-0.07,+0.08),
the high energy photon index beta = -2.71 (-0.30,+0.20),
the peak energy Ep = 315 (-24,+24) keV,
chi2 = 113/95 dof.

The spectrum near the peak count rate (measured from T0+0.256
to T0+3.072 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 = -0.55 (-0.10,+0.12),
the high energy photon index beta = -2.48 (-0.28,+0.18),
the peak energy Ep = 325 (-36,+40) keV,
chi2 = 96/84 dof.

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
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