TITLE: GCN CIRCULAR NUMBER: 22743 SUBJECT: Konus-Wind observation of GRB 180523A DATE: 18/05/29 14:07:26 GMT FROM: Anna Kozlova at Ioffe Institute A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 180523A (IPN Triangulation: Hurley et al., GCN Circ. 22740) triggered Konus-Wind at T0=66028.802 s UT (18:20:28.802). The burst light curve shows a bright main pulse lasting about 35 s, which is followed by a fainter second episode which started at ~T0+87.4 s and lasted up to ~T0+87.9 s. The emission in the main pulse is seen up to ~2 MeV. As observed by Konus-Wind, the burst had a fluence of 1.06(-0.08,+0.08)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+12.368 s, of 1.11(-0.22,+0.22)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the main episode (measured from T0 to T0+36.608 s) is best fit in the 20 keV - 2 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.69(-0.06,+0.07), the high energy photon index beta = -2.68(-0.30,+0.19), the peak energy Ep = 307(-17,+18) keV (chi2 = 49/61 dof). The spectrum near the maximum count rate (measured from T0+12.288 to T0+14.080 s) is best fit in the 20 keV - 2 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.51(-0.14,+0.16), the high energy photon index beta = -2.66(-0.89,+0.29), the peak energy Ep = 325(-39,+49) keV (chi2 = 53/55 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180523_T66028/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.