TITLE: GCN CIRCULAR NUMBER: 20995 SUBJECT: Konus-Wind observation of GRB 170405A DATE: 17/04/06 14:57:40 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 170405A (Swift-BAT detection: Troja et al.,GCN 20984; Fermi-GBM detection: Hui & Meegan., GCN 20986; Fermi-LAT detection: Vianello & Kocevski, GCN 20987) triggered Konus-Wind at T0=67181.254 s UT (18:39:41.254) The light curve shows a multi-peaked structure with a total duration of ~100 s and a hint of a subsequent weak/soft emission lasting until ~T0+200 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of (1.05 ± 0.12)x10^-4 erg/cm2 and a 64-ms peak energy flux, measured from T0+15.744, of (5.9 ± 0.9)x10^-6 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+73.984 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 = -0.53 (-0.17,+0.19), the high energy photon index beta = -2.36 (-0.25,+0.15), the peak energy Ep = 244 (-27,+32) keV, chi2 = 98/96 dof. The spectrum near the peak count rate (measured from T0+8.448 s to T0+24.832 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 = -0.54 (-0.22,+0.24), the high energy photon index beta = -2.56 (-1.02,+0.27), the peak energy Ep = 265 (-36,+51) keV, chi2 = 71/96 dof. Assuming the redshift z=3.510 (de Ugarte Postigo et al., GCN 20990) 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 ~2.6x10^54 erg, the peak luminosity L_iso is ~6.6x10^53 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is ~1100 keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB170405_T67181/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary. [GCN OPS NOTE(06apr17): Per author's request, in the first paragraph the V&K CirNum was changed from "20827" to "20987", and in the 6th paragraph the de Ugarte Postigo CircNum was changed from "20104" to "20990".]