TITLE: GCN CIRCULAR NUMBER: 29084 SUBJECT: Konus-Wind detection of GRB 201216C DATE: 20/12/18 14:50:32 GMT FROM: Dmitry Frederiks at Ioffe Institute 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.