TITLE: GCN CIRCULAR NUMBER: 20831 SUBJECT: Konus-Wind observation of GRB 170306B DATE: 17/03/07 11:39:11 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 170306B (Fermi-LAT detection: Omodei et al., GCN 20826; Fermi-GBM detection: Veres et al., GCN 20827) triggered Konus-Wind at T0=50850.920 s UT (14:07:30.920) The light curve shows a multi-peaked structure with a total duration of ~25 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of (3.4 ± 0.4)x10^-5 erg/cm2 and a 64-ms peak energy flux, measured from T0+3.712, of (4.1 ± 0.6)x10^-6 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+22.528 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 = -0.58 (-0.13,+0.16), the high energy photon index beta = -2.62 (-0.61,+0.28), the peak energy Ep = 237 (-27,+27) keV, chi2 = 105/97 dof. The spectrum near the peak count rate (measured from T0 to T0+6.912 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 = -0.40 (-0.11,+0.12), the high energy photon index beta = -2.70 (-0.84,+0.29), the peak energy Ep = 214 (-24,+30) keV, chi2 = 120/97 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170306_T50850/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.