GCN Circular 20111

D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 161023A (INTEGRAL detection: Mereghetti et al., GCN 20103
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triggered Konus-Wind at T0=81552.321 s UT (22:39:12.321).

The light curve shows a broad emission pulse with a duration
of ~50 s. The emission is seen up to ~6 MeV.

As observed by Konus-Wind, the burst had a fluence of
(4.2 �� 0.6)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0-8.320, of (5.3 �� 0.8)x10^-6 erg/cm2
(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 - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -1.11 (-0.18,+0.22),
the high energy photon index beta = -2.27 (-0.32,+0.16),
the peak energy Ep = 163 (-28,+37) keV,
chi2 = 81/97 dof.

The spectrum near the peak count rate (measured from T0 to T0+8.448 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 = -0.55 (-0.28,+0.34),
the high energy photon index beta = -2.16 (-0.24,+0.14),
the peak energy Ep = 172 (-28,+43) keV,
chi2 = 89/97 dof.


Assuming the redshift z=2.708 (Tanvir et al., GCN 20104
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and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.3, and Omega_Lambda = 0.7,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~6.8x10^53 erg,
the peak luminosity L_iso is ~3.2x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~640 keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB161023_T81552/

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