GCN Circular 29358

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

The long-duration, bright GRB 210121A
(Insight-HXMT/HE detection: Xue et al., GCN Circ. 29346
Not found
 
 

GECAM detection: Peng et al., GCN Circ. 29347
Not found
 
 
;
IPN triangulation: Hurley et al., GCN Circ. 29348
Not found
 
 
)
triggered Konus-Wind at T0=67306.174 s UT (18:41:46.174).

The burst light curve shows a multipeaked structure
which starts at ~T0-0.1 s and has a total duration of ~64 s.
The emission is seen up to ~7 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210121_T67306/

As observed by Konus-Wind, the burst
had a fluence of 1.18(-0.10,+0.10)x10^-4 erg/cm2,
and a 64-ms peak flux, measured from T0+1.072 s,
of 3.00(-0.43,+0.43)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+22.784 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 = -0.59(-0.05,+0.06),
the high energy photon index beta = -3.03(-1.42,+0.43),
the peak energy Ep = 875(-69,+70) keV
(chi2 = 110/97 dof).

The spectrum near the maximum count rate
(measured from T0+0.256 s to T0+1.792 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 = -0.32(-0.08,+0.09),
the high energy photon index beta = -3.60(3.60,+0.68),
the peak energy Ep = 981(-88,+94) keV
(chi2 = 82/97 dof).

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