TITLE: GCN CIRCULAR NUMBER: 14356 SUBJECT: Konus-Wind observation of GRB 130320B DATE: 13/03/30 11:59:08 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The very long intense GRB 130320B (IPN triangulation: Hurley et al., GCN 14354) triggered Konus-Wind at T0=48251.726s UT (13:24:11.726) The burst consists of three emission episodes with a total duration of ~380 s. The first episode (from ~T0-1 to ~T0+15s) shows very bright multi-peaked pulse with strong hard-to-soft spectral evolution. The second episode is a single weak soft-spectrum pulse from T0+135 to T0+175s. The third episode (from ~T0+195 to ~T0+380s) also shows a single pulse, more intense and harder than the second one. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB130320_T48251/ As observed by Konus-Wind, the burst had a total fluence of (7.8 ± 0.3)x10-5 erg/cm2, and a 64-ms peak flux, measured from T0+0.704s, of (7.2 ± 1.8)x10-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+384.768 s) is best fit in the 20 keV - 15 MeV range by a simple power law with the photon index 2.24 ± 0.03, chi2 = 85.5/98 dof. The spectrum at the onset of the burst (measured from T0 to T0+0.256 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 = -1.0 ± 0.3, the high energy photon index beta = -2.0 ± 0.3, the peak energy Ep = 340 ± 190 keV, chi2 = 23/25 dof. The average spectrum of the second emission episode (measured from T0+139.008 to T0+188.160 s) is best fit in the 20 keV - 2 MeV range by a power law with exponential cutoff model, for which: alpha = -1.7 ± 0.3, and Ep = 46 ± 23 keV, chi2 = 47/58 dof. The average spectrum of the third emission episode (measured from T0+294.656 to T0+384.768 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 = -1.23 ± 0.17, the high energy photon index beta = -2.25 ± 0.19, the peak energy Ep = 156 ± 29 keV, chi2 = 91.6/96 dof. All the quoted results are preliminary.