TITLE: GCN CIRCULAR NUMBER: 17207 SUBJECT: Konus-Wind observation of GRB 141220A DATE: 14/12/21 12:57:37 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lyssenko, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 141220A (Swift-BAT trigger #621915: Cummings et al., GCN 17196; Stamatikos et al., GCN 17202; Fermi-GBM observation: Yu, GCN 17205) triggered Konus-Wind at T0=21771.666 s UT (06:02:51.666). The KW light curve shows a single emission episode lasting from ~T0-0.5 s to ~T0+7.5 s. The emission in this episode is visible up to ~4 MeV. As observed by Konus-Wind, the burst had a fluence of 4.7(-0.4,+0.5)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0, of 2.2(-0.4,+0.5)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by the cutoff power law with the following model parameters: the photon index alpha = -0.55(-0.26,+0.30), and the peak energy Ep = 139(-14,+18) keV, chi2 = 83/98 dof. Fitting this spectrum with the Band model yields the same values of alpha and Ep and an upper limit on beta of -2.0 The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB141220_T21771/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.