TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4238 SUBJECT: Konus-Wind observation of GRB 051109A DATE: 05/11/09 23:00:13 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: The long soft GRB 051109A (Swift-BAT trigger #163136; Tagliaferri et al., GCN 4213, E. Fenimore et al., GCN 4217) triggered Konus-Wind at T0= 4342.541 s UT (01:12:22.541). As observed by Konus-Wind it had a single pulse with a duration about ~11 sec and a long decaying tail. This tail was seen up to ~130 sec after T0. The preliminary analysis of the Konus-Wind data gave the burst fluence 4.0(-3.4, +0.3)10^-6 erg/cm2,and peak flux on 256-ms time scale 5.8(-4.9, +0.3)10^-7 erg/cm2/sec (both in the 20 - 500 keV energy range). These values are very uncertain due to weakness and softness of the burst. The K-W spectrum integrated over the most intense part of the GRB (from T0 to T0+8.448 s) is well fitted (in the 20 - 500 keV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha) * exp(-E/E0) with alpha = 1.25 (-0.59, +0.44) and E0 = 213 (-126, +246) keV (chi^2 = 56/56 dof). The peak energy Ep = 161 (-58, +224) keV. All the quoted errors are at the 90% confidence level. Assuming z = 2.346 (Quimby et al., GCN 4221) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda = 0.7, the isotropic energy release is E_iso ~5x10^52 erg, the maximum luminosity is (L_iso)_max ~2.4x10^52 erg/s. Further analysis and refinement is in progress.