GCN Circular 43611

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 260121A
(IPN triangulation: Kozyrev et al., GCN 43564
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triggered Konus-Wind at T0=8549.319 s UT (02:22:29.319).

The burst light curve shows a single pulse
which starts at ~T0-0.5 s and has a total duration of ~21.6 s.
The emission is seen up to ~4 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB260121_T08549/

As observed by Konus-Wind, the burst
had a fluence of 2.79(-0.46,+0.47)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.512 s,
of 2.09(-0.31,+0.32)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+10.240 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 = -0.82(-0.11,+0.13),
the high energy photon index beta = -2.07(-0.33,+0.18),
the peak energy Ep = 366(-60,+75) keV
(chi2 = 97/97 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+2.304 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 = -0.75(-0.12,+0.15),
the high energy photon index beta = -1.78(-0.11,+0.09),
the peak energy Ep = 367(-73,+90) keV
(chi2 = 123/97 dof).

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.