TITLE: GCN CIRCULAR NUMBER: 26637 SUBJECT: Konus-Wind observation of GRB200101A DATE: 20/01/05 21:44:21 GMT FROM: Anastasia Tsvetkova at Ioffe Institute A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Lysenko, A. Ridnaia and T. Cline on behalf of the Konus-Wind team, report: The long-duration, hard-spectrum, very bright GRB200101A (Fermi GBM detection: Veres & Meegan, GCN 26627; AstroSat CZTI detection: Gaikwad et al., GCN 26632; IPN triangulation: Hurley et al., GCN 26635) triggered Konus-Wind at T0=74367.095 s UT (20:39:27.095). The burst light curve shows a a double-peaked structure which starts at ~T0-8.3 s and has a total duration of~81.8 s The emission is seen up to ~20 MeV. As observed by Konus-Wind, the burst had a fluence of 1.43(-0.09,+0.09)x10^-4 erg/cm2, and a 64-ms peak energy flux, measured from T0+7.776 s, of 1.12(-0.12,+0.12)x10^-4 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+17.408 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 = -0.74(-0.06,+0.07), the high energy photon index beta = -2.45(-0.23,+0.16), the peak energy Ep = 552(-46,+49) keV, chi2 = 103/97 dof. The spectrum near the peak count rate (measured from T0+7.680 to T0+7.936 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 = -0.43(-0.15,+0.18), the high energy photon index beta = -2.06(-0.15,+0.11), the peak energy Ep = 610(-105,+124) keV, chi2 = 50/55 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB200101_T74367/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.