TITLE: GCN CIRCULAR NUMBER: 25868 SUBJECT: Konus-Wind observation of GRB 190928A DATE: 19/09/30 11:29:55 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, A. Kozlova, A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long, very bright GRB 190928A (AGILE/MCAL detection: Ursi et al., GCN 25859; IPN triangulation: Hurley et al., GCN 25864; CALET Gamma-Ray Burst Monitor detection: Pal'shin et al., GCN 25865) triggered Konus-Wind (KW) at T0=47536.665 s UT (13:12:16.665). The burst light curve starts with a smooth pulse, which was followed, after a period of low-level emission, by a much more intense, multi-peaked emission complex. The total duration of the burst is ~195 s. The emission is seen up to ~15 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB190928_T47536/ As observed by Konus-Wind, the burst had a fluence of (4.9 ± 0.3)x10^-4 erg/cm^2 and a 256-ms peak energy flux, measured from T0+103.168, of (9.0 ± 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+185.334 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.98 (-0.07,+0.07), the high energy photon index beta = -1.97 (-0.13,+0.07), the peak energy Ep = 591 (-88,+108) keV, chi2 = 89/97 dof. The spectrum near the peak count rate (measured from T0+103.168 s to T0+103.424 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.72 (-0.25,+0.26), the high energy photon index beta = -1.73 (-0.24,+0.09), the peak energy Ep = 636 (-232,+754) keV, chi2 = 72/57 dof. All the quoted errors are estimated at the 90% confidence level. All the presented results are preliminary.