TITLE: GCN CIRCULAR NUMBER: 17703 SUBJECT: Konus-Wind observation of a bright burst from SGR 1935+2154 DATE: 15/04/14 15:02:18 GMT FROM: Dmitry Frederiks 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: A bright, short-duration, soft burst which is likely originated from SGR 1935+2154 (IPN triangulation: Golenetskii et al., GCN 17699) triggered Konus-Wind at T0=41064.683 s UT (11:24:24.683). The light curve shows a single pulse with a sharp(<10 ms) rise and a total duration of ~1.7 s. The emission is seen up to ~200 keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/SGRs/150412_T41064/ As observed by Konus-Wind, the burst had a fluence of 2.60(-0.03,+0.03)x10^-5 erg/cm2, and a 16-ms peak flux, measured from T0+0.800 s, of 2.3(-0.1,+0.1)x10^-5 erg/cm2/s (both in the 20 - 200 keV energy range). The time-averaged spectrum (measured from T0 to T0+9.472 s) is best fit in the 20 - 250 keV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = +0.21(-0.13,+0.13), and Ep = 36.5(-0.6,+0.6) keV (chi2 = 28.6/31 dof). A double blackbody fit to this spectrum yields the lower temperature kT1 = 6.4 (-0.7,+0.7) keV and the higher temperature kT2 = 12.3 (-0.6,+0.7) keV (chi2=36.3/30 dof). The rather long duration of the burst along with the large measured energy fluence put the burst in the class of "intermediate" SGR bursts. The measured spectral parameters are in typical range for bright short and intermediate SGR bursts; also, they resemble the fits reported by Swift/BAT and Fermi/GBM for much weaker and shorter bursts detected during the recent SGR 1935+2154 activity in February, 2015 (Lien et al., GCN 17490; Burns & Younes, GCN 17496). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.