TITLE: GCN CIRCULAR NUMBER: 16025 SUBJECT: Konus-Wind observation of GRB 140320D DATE: 14/03/21 17:15:12 GMT FROM: Dmitry Svinkin at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, and T. Cline on behalf of the Konus-Wind team, report: A very intense, long-duration, hard-spectrum GRB 140320D (IPN triangulation: K. Hurley et al., GCN 16023) triggered Konus-Wind at T0=73298.804 s UT (20:21:38.804). The burst light curve shows a bright, double-peaked pulse with a total duration of ~50 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of (2.1 +/- 0.1)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+15.456 s, of (6.7 +/- 0.7)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+45.568 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.83 (-0.03,+0.03), the high energy photon index beta = -2.75 (-0.32,+0.20), the peak energy Ep = 575 (-30,+32) keV, chi2 = 100/87 dof. The spectrum near the maximum count rate (measured from T0+15.360 to T0+15.872 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.30 (-0.11,+0.13), the high energy photon index beta = -2.59 (-0.62,+0.30), the peak energy Ep = 655 (-89,+102) keV, chi2 = 82/56 dof. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB140320_T73298/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.