GCN Circular 35359

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 GRB 231210B (Swift detection: Page et al., GCN 35314
Not found
 
 
)
triggered Konus-Wind (KW) at T0=77347.988 s UT (21:29:07.988).

The burst light curve shows a multi-peaked structure
with a total duration of of ~9 s.
The emission is seen up to ~0.5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB231210_T77347/

As observed by Konus-Wind, the burst had
a total fluence of (4.02 ± 0.56)x10^-6 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+2.944 s,
of (2.19 ± 0.32)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by a power law with exponential
cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.62(-0.37,+0.44) and Ep = 174(-27,+40) keV (chi2 = 65/87 dof).
Fitting this spectrum by a Band function yields the same values of alpha and Ep,
and an upper limit on the high energy photon index beta of -2.5 (chi2 = 65/86 dof).

Assuming the redshift z=3.13 (Saccardi et al., GCN 35317
Not found
 
 
)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the burst isotropic energy release E_iso to (8.8 ± 1.3)x10^52 erg,
the isotropic peak luminosity L_iso to (2.0 ± 0.3)x10^53 erg/s,
the rest-frame peak energy of the spectrum Ep,z to ~720 keV.
With the obtained estimates, GRB 231210B is inside 90% prediction band for
the 'Amati' relation and inside 68% prediction band for the 'Yonetoku' relation
derived for the sample of >300 long KW GRBs with known redshifts
(Tsvetkova et al., 2017; Tsvetkova et al., 2021), see
http://www.ioffe.ru/LEA/GRBs/GRB231210_T77347/GRB231210B_rest_frame.pdf

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.