TITLE: GCN CIRCULAR NUMBER: 15452 SUBJECT: Konus-Wind observation of GRB 131105A DATE: 13/11/05 11:18:56 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 131105A (Swift-BAT trigger 576738: Cummings et al., GCN 15446) triggered Konus-Wind at T0=7527.233 s UT (02:05:27.233). The burst light curve shows multiple peaks in the time interval from ~T0-35 s till ~T0+90 s. The emission is seen up to ~3 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB131105_T07527/ As observed by Konus-Wind, the burst had a fluence of (2.3 ± 0.2)x10-5 erg/cm2, and a 64-ms peak flux, measured from T0+1.600 s, of (2.0 ± 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+90.368 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 = -0.88 ± 0.38, the high energy photon index beta = -2.33 ± 0.33, the peak energy Ep = 156 ± 38 keV, chi2 = 97/96 dof. The spectrum near the maximum count rate (measured from T0 to T0+8.448 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 = -1.04 ± 0.27, the high energy photon index beta = -2.64 ± 0.76, the peak energy Ep = 174 ± 41 keV, chi2 = 87.9/97 dof. Assuming the redshift z=1.686 (Xu, et al., GCN 15450) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73, we estimate the following rest-frame parameters: the isotropic energy release E_iso is (1.7 ± 0.1)x10^53 erg, the peak luminosity L_iso is (4.0 ± 0.4)x10^52 erg/s, and the rest-frame peak energy Ep,i = (420 ± 100) keV All the quoted values are preliminary.