TITLE: GCN CIRCULAR NUMBER: 19649 SUBJECT: Konus-Wind observation of GRB 160703A DATE: 16/07/04 11:31:52 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 160703A (Swift/BAT observation: Cenko et al., GCN 19645; Lien et al., GCN 19648) triggered Konus-Wind at T0=43807.015 s UT (12:10:07.015). The light curve shows multiple overlapping pulses, a total duration of the burst is ~50 s. The emission is seen up to ~4 MeV. As observed by Konus-Wind, the burst had a fluence of (2.7 ± 0.2)x10^-5 erg/cm2 and a 64-ms peak energy flux, measured from T0+23.360, of (2.8 ± 0.3)x10^-6 erg/cm2 (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+41.216 s) is best fit in the 20 keV - 10 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha = -1.01(-0.09,+0.10), and the peak energy Ep = 327(-36,+46) keV, chi2 = 93/97 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep with only an upper limit on beta of -2.4, chi2 = 93/96 dof. The spectrum near the peak count rate (measured from T0 to T0+41.216 s) is best fit in the 20 keV - 10 MeV range by a cutoff power-law (CPL) function with the following model parameters: the photon index alpha = -0.66(-0.15,+0.16), and the peak energy Ep = 272(-29,+35) keV, chi2 = 79/89 dof. Fitting this spectrum with the GRB (Band) function yields the same alpha and Ep with only an upper limit on beta of -3.1, chi2 = 79/88 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160703_T43807/ All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.