GCN Circular 38100

V. Panteleeva, D. Frederiks, A. Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long-duration GRB 241021A
(IPN triangulation: Kozyrev et al., GCN 37847
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triggered Konus-Wind at T0=53930.240 s UT (14:58:50.240).

The burst light curve shows a multipeaked structure
which starts at ~T0-25 s and has a total duration of ~236 s.
The emission is seen up to ~16 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB241021_T53930/

As observed by Konus-Wind, the burst
had a fluence of 2.62(-0.21,+0.23)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+15.616 s,
of 6.42(-1.49,+1.50)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+224 s)
is best fit in the 20 keV - 16 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.09(-0.04,+0.04),
the high energy photon index beta = -2.76(-0.60,+0.29),
the peak energy Ep = 359(-25,+26) keV
(chi2 = 103/97 dof).

The spectrum near the maximum count rate
(measured from T0+15.360 to T0+21.504 s)
is best fit in the 20 keV - 16 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.05(-0.07,+0.07),
the high energy photon index beta = -2.54(-0.58,+0.26),
the peak energy Ep = 474(-60,+71) keV
(chi2 = 102/97 dof).

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