TITLE: GCN CIRCULAR NUMBER: 17808 SUBJECT: Konus-Wind observation of GRB 150510A DATE: 15/05/11 17:23:27 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: The long-duration, hard-spectrum, intense GRB 150510A (Fermi-LAT detection: Vianello & Racusin, GCN 17805; Racusin et al., GCN 17806; Fermi-GBM detection: Burns & Meegan GCN 17807) triggered Konus-Wind at T0=11988.505 s UT (03:19:48.505). The KW light curve shows a FRED-like structure with a duration of ~62 s. The emission is visible up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150510_T11988/ As observed by Konus-Wind, the burst had a fluence of 1.9(-0.1,+0.1)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+0.064 s, of 4.0(-0.3,+0.3)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+39.168 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.99 (-0.04,+0.05), the high energy photon index beta = -2.81 (-1.10,+0.37), the peak energy Ep = 1253 (-129,+134) keV, chi2 = 106/95 dof. The spectrum near the peak count rate (measured from T0 to T0+6.400 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -0.74(-0.05,+0.05), and the peak energy Ep = 1320(-85,+93) keV, chi2 = 100/87 dof. Fitting this spectrum with the Band model yields the same values of alpha and Ep with an upper limit on the high-energy photon index beta of -2.9 All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.