TITLE: GCN CIRCULAR NUMBER: 17870 SUBJECT: Konus-Wind observation of GRB 150523A DATE: 15/05/25 12:47:10 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 150523A (Fermi-GBM detection: Yu, GCN Circ. 17863; Fermi-LAT detection: Bissaldi, et al., GCN Circ. 17864) triggered Konus-Wind at T0=34189.641 s UT (09:29:49.641). The burst light curve consists of two pulses with a total duration of ~36 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/GRB150523_T34189/ As observed by Konus-Wind, the burst had a fluence of 4.44(-0.69,+0.71)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+31.792 s, of 5.52(-1.52,+1.53)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+41.216 s) is best fit in the 20 keV - 12 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.31(-0.14,+0.16), the high energy photon index beta = -2.66(-0.99,+0.32), the peak energy 399(-42,+52) keV (chi2 = 94/97 dof) The spectrum near the maximum count rate (measured from T0+24.832 to T0+33.024 s) is best fit in the 20 keV - 12 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.35(-0.15,+0.17), the high energy photon index beta = -2.66(-1.35,+0.34), the peak energy 389(-48,+58) keV (chi2 = 104/97 dof) All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.