TITLE: GCN CIRCULAR NUMBER: 16679 SUBJECT: Konus-Wind observation of GRB 140810A DATE: 14/08/11 09:25:04 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 140810A (Fermi-LAT detection: Moretti et al., GCN 16678) triggered Konus-Wind at T0=67571.433 s UT (18:46:11.433). The light curve shows a multi-peaked structure with a total duration of ~100 s. The emission is seen up to 10 MeV. As observed by Konus-Wind, the burst had a fluence of 1.5(-0.1,+0.1)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+23.104 s, of 1.3(-0.1,+0.1)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+93.696 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 = -1.05 (-0.06,+0.05), the high energy photon index beta = -2.35 (-0.16,+0.12), the peak energy Ep = 239 (-26,+25) keV, chi2 = 105/97 dof. The spectrum near the peak count rate (measured from T0+16.640 to T0+29.959 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 = -0.86 (-0.10,+0.10), the high energy photon index beta = -2.44 (-0.35,+0.17), the peak energy Ep = 416 (-47,+63) keV, chi2 = 87/97 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB140810_T67571/ All the quoted errors are at the 90% sigma confidence level. All the quoted values are preliminary.