TITLE: GCN CIRCULAR NUMBER: 15619 SUBJECT: Konus-Wind observation of GRB 131226A DATE: 13/12/27 14:44:44 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 131226A (Swift-BAT trigger 582123: Oates, et al., GCN 15612; Stamatikos, et al. GCN 15613) triggered Konus-Wind at T0=20858.013 s UT (05:47:38.013). The burst light curve shows a multi-peaked structure with a total duration of ~7 s. As observed by Konus-Wind, the burst had a fluence of 1.01(-0.07,+0.08)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+2.704 s, of (5.0 +/- 1.0)x10^-5 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 well fitted (in the 20 keV - 2 MeV range) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), with alpha = -0.90(-0.12,+0.13), and Ep = 264(-17,+20) keV (chi2 = 65.6/60 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and only an upper limit on the high energy photon index: beta < -2.5. All the quoted values are preliminary. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB131226_T20858/