TITLE: GCN CIRCULAR NUMBER: 22284 SUBJECT: Konus-Wind observation of GRB 171216B DATE: 17/12/25 15:37:42 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, hard-spectrum GRB 171216B (IPN triangulation: Hurley et al., GCN circ. 22263; CALET-CGBM detection: Pal'shin et al., GCN circ. 22268) triggered Konus-Wind at T0=51948.499 s UT (14:25:48.499). The burst light curve shows a multipeaked structure which starts at ~T0-0.3 s and has a total duration of ~7.4 s. The emission is seen up to ~5 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB171216_T51948/ As observed by Konus-Wind, the burst had a fluence of 1.59(-0.29,+0.37)x10^-5 erg/cm2, and a 16-ms peak flux, measured from T0+0.034 s, of 2.32(-1.00,+1.15)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.11(-0.11,+0.13) and Ep = 1341(-412,+673) keV (chi2 = 85/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.3 (chi2 = 85/97 dof). The spectrum near the maximum count rate (measured from T0 to T0+0.064 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: with alpha = -0.34(-0.37,+0.52) and Ep = 994(-372,+539) keV (chi2 = 15/16 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.2 (chi2 = 15/15 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.