TITLE: GCN CIRCULAR NUMBER: 17344 SUBJECT: Konus-Wind observation of GRB 150118B DATE: 15/01/22 11:30:17 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, hard-spectrum, intense GRB 150118B (Fermi-LAT detection: Kocevski et al., GCN 17307; Fermi-GBM detection: Stanbro, GCN 17308; IPN triangulation: Hurley et al., GCN 17342) triggered Konus-Wind at T0=35302.394 s UT (09:48:22.394). The light curve shows multiple emission episodes from ~T0-8 s to ~T0+60 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/GRB150118_T35302/ As observed by Konus-Wind, the burst had a fluence of 1.87(-0.15,+0.14)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+39.680 s, of 1.88(-0.18,+0.20)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+58.368 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -0.98(-0.04,+0.04), and the peak energy Ep = 695(-42,+47) keV, chi2 = 103/97 dof. Fitting this spectrum with the Band model yields the same values of alpha and Ep with an upper limit on beta of -2.8 The spectrum near the peak count rate (measured from T0+35.328 to T0+41.984 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -0.84(-0.08,+0.08), and the peak energy Ep = 614(-55,+64) keV, chi2 = 115/98 dof. All the quoted errors are at the 90% sigma confidence level. All the quoted values are preliminary.