TITLE: GCN CIRCULAR NUMBER: 17802 SUBJECT: Konus-Wind observation of GRB 150428A DATE: 15/05/04 14:55:51 GMT FROM: Dmitry Svinkin 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 150428A (Swift-BAT trigger #639275: Page, et al., GCN Circ. 17765; Baumgartner, et al., GCN Circ. 17774) was detected by Konus-Wind in the waiting mode. The burst light curve shows a single pulse which started approximately at BAT trigger time T0(BAT) and has a duration of ~45 s. As observed by Konus-Wind, the burst had a fluence of 1.61(-0.09,+0.10)x10^-5 erg/cm2 and a 2.944-s peak flux, measured from ~T0(BAT)+21 s, of 5.5(-0.7,+0.9)x10^-7 erg/cm2 (both in the 20 - 1200 keV energy range). Modelling the K-W 3-channel time-integrated spectrum (from T0(BAT)-3 s to T0(BAT)+41 s) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.04(-0.12,+0.14), and Ep = 275(-29,+37) keV. All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary. The K-W light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB150428A/