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GCN Circular 29084

Subject
Konus-Wind detection of GRB 201216C
Date
2020-12-18T14:50:32Z (3 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, R.Aptekar, A.Lysenko,
A. Ridnaia, D. Svinkin, A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 201216C (Swift detection:  Beardmore et al., GCN 29061;
Fermi GBM detection:  Malacaria et al., GCN 29071;
AstroSat CZTI detection:  Nadella et al., GCN 29074;
MAGIC detection:  Blanch et al., GCN 29075)
triggered Konus-Wind (KW) at T0=83248.844 s UT (23:07:28.844).

The burst light curve shows a multi-peaked structure with the total duration of ~40 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB201216_T83248/

As observed by Konus-Wind, the burst had
a fluence of (1.86 �� 0.10)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0+24.704,
of (1.82 �� 0.12)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+24.832 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 = -1.09 (-0.05,+0.06),
the high energy photon index beta = -2.32 (-0.13,+0.10),
the peak energy Ep = 333 (-28,+29) keV,
chi2 = 102/97 dof.

The spectrum near the peak count rate (measured from T0+18.944
to T0+26.368 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.99 (-0.05,+0.06),
the high energy photon index beta = -2.24 (-0.14,+0.10),
the peak energy Ep = 326 (-41,+47) keV,
chi2 = 121/97 dof.

Assuming the redshift z=1.1 (Vielfaure et al., GCN 29077)
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 following rest-frame parameters:
the isotropic energy release E_iso = (6.2 �� 0.6)x10^53 erg,
the peak luminosity L_iso = (1.3 �� 0.1)x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum Ep,z=(700 �� 61) keV.
With these values, GRB 201216C is within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations built for the sample
of long KW GRBs with known redshifts (part I: Tsvetkova et al., ApJ 850 161, 2017;
part II: Tsvetkova et al., ApJ, submitted),
see http://www.ioffe.ru/LEA/GRBs/GRB201216_T83248/GRB201216C.pdf


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