TITLE: GCN CIRCULAR NUMBER: 10817 SUBJECT: Konus-Wind observation of GRB 100528A DATE: 10/05/31 15:33:58 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long GRB 100528A localized by SuperAGILE (Del Monte et al., GCN 10810) triggered Konus-Wind at T0=6483.610 s UT (01:48:03.610). The burst light curve shows a main pulse with a duration of ~30 s followed by a much weaker and softer pulse at ~T0+44 s with a duration of ~15 s. As observed by Konus-Wind the burst had a fluence of 2.85(-0.19, +0.21)x10^-5 erg/cm2, and a 256-ms peak flux measured from T0+6.688 s of 3.99(-0.58, +0.59)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+23.296 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 = -1.28(-0.06, +0.07), and Ep = 382(-52, +69) keV (chi2 = 55.0/61 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and only an upper limit on the high energy photon index: beta < -2.28 (chi2 = 55.0/60 dof). The spectrum accumulated over the burst maximum (from T0 to T0+6.912 s) is well fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model with alpha = -1.18 +/- 0.07, and Ep = 558(-85, +115) keV (chi2 = 71.4/61 dof). Fitting by GRB (Band) model yields the same alpha and Ep, and only an upper limit on the high energy photon index: beta < -2.43 (chi2 = 71.4/60 dof). All the quoted errors are at the 90% confidence level. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB100528_T06483/