GCN Circular 29424

D. Frederiks, on behalf of the Konus-Wind team:

The KW spectral data and energetics of GRB 210204A
reported in Frederiks et al., GCN 29415
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  contain errors due to an
incorrect detector response matrix used in the calculations.
The correct spectra and energetics are provided below,
we are sorry for the inconvenience.

The burst time-integrated spectrum (measured from T0 to T0+49.408 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.45 (-0.08,+0.09),
the high energy photon index beta = -2.63 (-0.41,+0.20),
the peak energy Ep = 136 (-16,+21) keV,
chi2 = 76/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.12 (-0.18,+0.34),
the high energy photon index beta = -2.45 (-0.46,+0.26),
the peak energy Ep = 175 (-42,+34) keV,
chi2 = 104/96 dof.

As observed by Konus-Wind, the burst had
a fluence of (7.0 �� 0.9)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+2.304,
of (5.2 �� 0.9)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

Assuming the redshift z=1.466 (Izzo et al., GCN 29411
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 )
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 isotropic energy release E_iso to ~3.9x10^53 erg,
the isotropic luminosity L_iso to ~7.1x10^52 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z to ~333 keV.
With these values, GRB 210204A is within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., ApJ, in press),
see http://www.ioffe.ru/LEA/GRBs/GRB210204_T23570/GRB210204A_rest_frame.pdf


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