TITLE: GCN CIRCULAR NUMBER: 20111 SUBJECT: Konus-Wind observation of GRB 161023A DATE: 16/10/24 17:04:57 GMT FROM: Dmitry Frederiks at Ioffe Institute 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) 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) 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.