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GCN Circular 23363

Konus-Wind observation of GRB 181020A
2018-10-22T14:49:57Z (6 years ago)
Anastasia Tsvetkova at Ioffe Institute <>
A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline
on behalf of the Konus-Wind team, report:

The�� GRB 181020A�� (Swift-BAT detection:
Moss et al., GCN 23349; Sakamoto�� et al., GCN 23357;
Fermi-LAT detection: Axelsson, GCN 23350;
Fermi GBM detection: Veres, GCN 23352)
triggered Konus-Wind at T0=68437.284 s UT (19:00:37.284).

The burst light curve shows a single pulse with a total duration of ~26 s.
The emission is seen up to ~5 MeV.

As observed by Konus-Wind, the burst
had a fluence of 4.17(-0.54,+0.58)x10^-5 erg/cm2,
and a 64-ms peak energy flux, measured from T0+7.552 s,
of 8.27(-1.99,+2.05)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum of the burst
(measured from T0 to T0+15.360 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.73(-0.11,+0.13),
the high energy photon index beta = -2.35(-0.41,+0.22),
the peak energy Ep = 371(-52,+57) keV,
chi2 = 80/97 dof.

Assuming the redshift z=2.938 (Fynbo et al., GCN 23356)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is 8.28(-1.07,+1.16)x10^53 erg,
the peak luminosity L_iso is 6.47(-1.56,+1.60)x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is 1461(-205,+225) keV.

The Konus-Wind light curve of this GRB is available at

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