TITLE: GCN CIRCULAR NUMBER: 9836 SUBJECT: Konus-Wind observations of GRB 090823 DATE: 09/08/25 10:11:26 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long GRB 090823 (Cummings et al., GCN 9835) triggered Konus-Wind at T0=58270.606 s UT (16:11:10.606) This burst was also observed by the Suzaku WAM, Agile-MCAL, and (during a slew maneuver) Swift-BAT. The burst had a smooth structure with a duration of ~10 s. The Konus-Wind light curves of this GRB are available at http://www.ioffe.ru/LEA/GRBs/GRB090823_T58270/ As observed by Konus-Wind the burst had a fluence of 8.9(-0.3,+0.5)x10-6 erg/cm2, and a 256-ms peak flux, measured from T0+3.072, of 2.8(-0.25,+0.25)x10-6 erg/cm2/s (both in the 20 keV - 2 MeV energy range). The time-integrated spectrum of the burst (from T0 to T0+14.848 s) is well fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with Alpha = -0.49(-0.15,+0.17), and Ep = 188(-15,+18)keV (chi2 = 56/61 dof). Fitting by the GRB (Band) model yields to the same Alpha and Ep values with the high energy photon index Beta of -7 (< -2.7) The spectrum at the maximum count rate, measured from T0 + 0.256s to T0 + 6.656s, is well fitted (in the 20 keV - 2 MeV range) by the GRB (Band) model with: Alpha = -0.45(-0.14,+0.16), Beta = -3.0(-2.2,+0.4), and Ep = 182(-18,+18)keV (chi2 = 63/60 dof). All the quoted values are preliminary. All the quoted errors are at the 90% confidence level.