TITLE: GCN CIRCULAR NUMBER: 23193 SUBJECT: Konus-Wind observation of GRB 180828A DATE: 18/08/30 20:51:39 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 180828A (Swift-BAT detection: Beardmore et al., GCN 23182; Markwardt et al., GCN 23188; Fermi-GBM observation: Roberts & Meegan, GCN 23183; AstroSat-CZTI detection: Khanam et al., GCN 23191) triggered Konus-Wind at T0=68250.016 s UT (18:57:30.016). The burst light curve shows a multipeaked structure which starts at ~T0-6 s and has a duration of ~14.7 s. The emission is seen up to ~10 MeV. As observed by Konus-Wind, the burst had a fluence of 4.41(-0.17,+0.17)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+7.456 s, of 1.57(-0.24,+0.26)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+15.104 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.50(-0.12,+0.12) and Ep = 341(-21,+24) keV (chi2 = 72/88 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.7 (chi2 = 70/87 dof). The spectrum near the maximum count rate (measured from T0+6.912 to T0+15.104 s) is best fit in the 20 keV - 10 MeV range by the CPL model with alpha = -0.36(-0.23,+0.26) and Ep = 395(-45,+59) keV (chi2 = 61/86 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.5 (chi2 = 61/85 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180828_T68250/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.