TITLE: GCN CIRCULAR NUMBER: 17055 SUBJECT: Konus-Wind observation of GRB 141109A DATE: 14/11/10 17:35:48 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, V. Pal'shin, D. Frederiks, P. Oleynik, M.Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team report: The most intense part of the long GRB 141109A (Swift-BAT trigger #618024: D'Avanzo, et al., GCN Circ. 17037, Baumgartner, et al., GCN Circ. 17044) was detected by Konus-Wind in the waiting mode. The burst light curve shows two pulses started at ~T0(BAT)+31 s with a total duration of ~94 s, and a weak tail seen in the soft energy range G1 up to ~T0(BAT)+300 s. As observed by Konus-Wind, the burst had a fluence of 1.37(-0.18,+0.20)x10^-5 erg/cm2 and a 2.944-s peak flux, measured from ~T0(BAT)+81 s, of (4.9 +/- 0.8)x10^-7 erg/cm2 (both in the 20 - 1200 keV energy range). Modeling the K-W 3-channel time-integrated spectrum (from T0(BAT)+31 s to T0(BAT)+125 s) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.24(-0.25,+0.37), and Ep = 191(-43,+76) keV. Assuming z = 2.993 (Xu et al., GCN 17040) and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, Omega_Lambda = 0.73, the isotropic energy release is E_iso = 3.31(-0.59,+0.78)x10^53 erg, and the isotropic peak luminosity is L_iso = (4.8 +/- 0.9)x10^52 erg/s in 1 keV to 10 MeV at the GRB rest frame extrapolating the best exponential cutoff function fit. All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary. The K-W light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB141109A/