TITLE: GCN CIRCULAR NUMBER: 22461 SUBJECT: Konus-Wind observation of GRB 180305A DATE: 18/03/06 14:42:58 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik, M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration, bright GRB 180305A (Fermi-LAT detection: Axelsson and E. Bissaldi, GCN Circ. 22457; Fermi-GBM detection: Veres and von Kienlin, GCN Circ. 22458) triggered Konus-Wind at T0=33967.647 s UT (09:26:07.647). The burst light curve shows a single emission episode which starts at ~T0-2.4 s and has a total duration of ~44 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180305_T33967/ As observed by Konus-Wind, the burst had a fluence of 8.43(-0.58,+0.59)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+3.168 s, of 2.02(-0.32,+0.32)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+16.128 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.51(-0.09,+0.10), the high energy photon index beta = -2.41(-0.17,+0.13), the peak energy Ep = 348(-27,+30) keV (chi2 = 139/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+4.352 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.25(-0.15,+0.17), the high energy photon index beta = -2.59(-0.44,+0.23), the peak energy Ep = 467(-56,+64) keV (chi2 = 113/81 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.