TITLE: GCN CIRCULAR NUMBER: 21280 SUBJECT: Konus-Wind observation of GRB 170626B DATE: 17/06/28 14:20:04 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 170626B (Insight-HXMT observation: Liu et al., GCN 21265; IPN triangulation: Kozlova et al., GCN 21279) triggered Konus-Wind at T0=3482.215 s UT (00:58:02.215). The burst light curve shows a multipeaked structure started at ~T0-6.1 s with a total duration of ~16.8 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of 4.12(-0.20,+0.22)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.256 s, of 1.03(-0.18,+0.18)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+14.592 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 = -0.59(-0.13,+0.14) and Ep = 423(-38,+45) keV (chi2 = 87/99 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.7 (chi2 = 87/98 dof) The spectrum near the maximum count rate (measured from T0+0.256 to T0+6.400 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model with alpha = -0.45(-0.11,+0.12) and Ep = 429(-30,+35) keV (chi2 = 91/92 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.8 (chi2 = 91/91 dof) The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170626_T03482/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.