TITLE: GCN CIRCULAR NUMBER: 12323 SUBJECT: Konus-Wind observation of GRB 110903A DATE: 11/09/03 14:21:13 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 very long GRB 110903A (localized by INTEGRAL: Mereghetti et al., GCN 12322) triggered Konus-Wind at T0=09573.115s UT (02:39:33.115) The light curve shows two equally hard peaks started at ~T0 and at ~T0+190s respectively, and a third, softer peak, started at ~T0+320s. A total duration of the burst is ~370 s. The emission is seen up to ~7 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB110903_T09573/ As observed by Konus-Wind the burst had a fluence of 4.2(-0.7,+2.2)x10-5 erg/cm2, and a 256-ms peak flux, measured from T0+196.352 s, of 1.8(-0.4,+0.6)x10-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+368.896 s) is best fitted in the 20 keV - 10 MeV range by a power law with exponential cutoff model, for which alpha = -0.96 (-0.29, +0.37), and Ep = 301(-80, +185) keV, chi2 = 77.8/88 dof. Fitting this spectrum by the GRB (Band) function yields the following model parameters: the low-energy photon index alpha = -0.93 (-0.31, +0.41), the high energy photon index beta = -2.7 (<-1.9), the peak energy Ep = 287(-89, +191) keV, chi2 = 77.6/87 dof. The spectrum near the maximum count rate (measured from T0+196.864 to T0+205.056 s) is best fitted in the 20 keV - 10 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = -0.69 (-0.20, +0.24), the high energy photon index beta = -2.7 (<-2.2), the peak energy Ep = 295(-57, +77) keV, chi2 = 95.3/87 dof. All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.