TITLE: GCN CIRCULAR NUMBER: 22227 SUBJECT: Konus-Wind observation of GRB 171205A DATE: 17/12/10 17:31:55 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report: The long GRB 171205A (Swift-BAT trigger #794972: (D'Elia et al., GCN 22177; Barthelmy et al., GCN 22184; T0(BAT)= 07:20:43.893 UT) was detected by Konus-Wind (KW) in the waiting mode. A bayesian block analysis of the KW waiting mode data reveals a count rate increase in the interval from ~T0(BAT)-50 s to ~T0(BAT)+95 s. The detection significance in the combined G1+G2 light curve (25-360 keV) is ~10 sigma (95 s scale) while no statistically significant emission has been detected in the G3 band (360-1470 keV). The KW light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB171205A/ The time-averaged 3-channel spectrum, measured from T0(BAT)-48.743 s to T0(BAT)+42.521 s, is well fit by a simple power-law (PL) model with the PL index 2.0 ± 0.18, chi2 = 0.88 for 1 dof. The burst fluence in the 20-1500 keV band is (7.8 ± 1.6)x10^-6 erg/cm^2. Assuming z = 0.0368 (Izzo et al., GCN 22180) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.30, and Omega_Lambda = 0.70, the burst isotropic energy release E_iso is 2.4x10^49 erg (20-1500 keV, observer frame). All the quoted errors are estimated at the 1 sigma confidence level. All the presented results are preliminary.