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GCN Circular 29424

Subject
Konus-Wind detection of GRB 210204A (correction to GCN 29415)
Date
2021-02-08T11:35:19Z (3 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
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 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)
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.
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