TITLE: GCN CIRCULAR NUMBER: 19312 SUBJECT: Konus-Wind observation of GRB 160409A DATE: 16/04/13 13:13:04 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-duration GRB 160409A (Swift-BAT ground detection: Evans et al., GCN 19304) triggered Konus-Wind at T0=21254.430 s UT (05:54:14.430). The KW light curve shows single structure-less pulse with a total duration of ~35 s. The emission is visible up to ~7 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160409_T21254/ As observed by Konus-Wind, the burst had a fluence of 1.8(-0.3,+0.3)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.846 s, of 1.5(-0.2,+0.2)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+24.832 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -0.68(-0.16,+0.18), and the peak energy Ep = 209(-18,+22) keV, chi2 = 107/98 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep with an upper limit on beta of -2.1 The spectrum near the peak count rate (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -0.72(-0.17,+0.19), and the peak energy Ep = 252(-26,+32) keV, chi2 = 122/98 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep with an upper limit on beta of -2.0 All the quoted errors are at the 1 sigma confidence level. All the quoted values are preliminary.