TITLE: GCN CIRCULAR NUMBER: 18074 SUBJECT: Konus-Wind observation of GRB 150724B DATE: 15/07/27 14:09:55 GMT FROM: Anastasia Tsvetkova 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, hard-spectrum GRB 150724B (Fermi-LAT detection: Bissaldi, Racusin & Moretti, GCN 18065; Fermi GBM detection: Veres, Connaughton & Meegan, GCN 18066) triggered Konus-Wind at T0=67574.792 s UT (18:46:14.792). The burst light curve shows a double-peaked structure which starts ~30 s before the trigger and has a total duration of ~41 s. The emission is seen up to ~5 MeV. As observed by Konus-Wind, the burst had a fluence of 3.63(-0.29,+0.69)x10^-5 erg/cm2, and a 64-ms peak energy flux, measured from T0+2.064 s, of 6.01(-1.60,+1.62)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Only the brightest part of the burst is covered by the KW triggered mode data and, therefore, available for the multi-channel spectral analysis. The time-averaged spectrum measured from T0 to T0+8.448 s is best fit in the 20 keV - 5 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.65(-0.11,+0.12), and Ep = 663(-69,+82) keV (chi2 = 77/73 dof). Fitting by the GRB (Band) function yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.0 (chi2 = 77/72 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150724_T67574/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.