TITLE: GCN CIRCULAR NUMBER: 17900 SUBJECT: Konus-Wind observation of GRB 150530A DATE: 15/06/03 17:40:38 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 GRB 150530A (Swift-BAT trigger #642018: Starling et al., GCN 17888; Markwardt et al., GCN 17890; Fermi GBM detection: Yu, Younes and Meegan, GCN 17891) triggered Konus-Wind at T0=42136.529 s UT (11:42:16.529). The burst light curve shows a single pulse lasting from ~T0-4 s to ~T0+6 s. The emission is seen up to ~1.2 MeV. As observed by Konus-Wind, the burst had a fluence of 2.54(-0.26,+0.28)x10^-6 erg/cm2, and a 64-ms peak energy flux, measured from T0+0.082 s, of 1.06(-0.43,+0.43)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 1.2 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.63(-0.38,+0.46), and Ep = 114(-17,+23) keV (chi2 = 59/58 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.07 (chi2 = 59/57 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150530_T42136/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.