TITLE: GCN CIRCULAR NUMBER: 22003 SUBJECT: Konus-Wind observation of GRB 171010A DATE: 17/10/12 11:50:56 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, very bright GRB 170410A (Fermi-LAT detection: Omodei et al., GCN 21985; Fermi-GBM detection: Poolakkil and Meegan, GCN 21992) triggered Konus-Wind at T0=68460.142 s UT (19:01:00.142) The burst light curve shows a bright, multi-peaked pulse, with a total duration of ~155 s (from ~T0-8 s -- ~T0+147 s), which was preceded by a weaker emission starting from ~T0-150 s. A much weaker pulse is also seen in the KW light curve around ~T0+250 s. The emission is seen up to ~15 MeV. As observed by Konus-Wind, the burst had a fluence of (6.5 ± 0.2)x10^-4 erg/cm2 and a 64-ms peak energy flux, measured from T0+26.496, of (2.45 ± 0.17)x10^-5 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+147.968 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 = -1.09 (-0.04,+0.04), the high energy photon index beta = -2.42 (-0.07,+0.06), the peak energy Ep = 171 (-6,+7) keV, chi2 = 95/95 dof. The spectrum near the peak count rate (measured from T0+26.112 s to T0+27.136 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 = -0.75 (-0.06,+0.06), the high energy photon index beta = -2.58 (-0.22,+0.16), the peak energy Ep = 273 (-27,+27) keV, chi2 = 78/70 dof. Assuming the redshift z=0.33 (Kankare et al., GCN 22002) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, and Omega_Lambda = 0.7, we estimate the following rest-frame parameters: the isotropic energy release E_iso is ~1.8x10^53 erg, the peak luminosity L_iso is ~8.8x10^51 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is ~227 keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB171010_T68460/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary. [GCN OPS NOTE(12oct17): Per author's request, the "170410A" in the first sentence was changed to "171010A".]