TITLE: GCN CIRCULAR NUMBER: 22770 SUBJECT: Konus-Wind observation of GRB 180611A DATE: 18/06/13 16:09:51 GMT FROM: Anastasia Tsvetkova at Ioffe Institute A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 180611A (IPN Triangulation: Hurley et al., GCN 22767; Fermi GBM observation: Bissaldi &  Meegan, GCN 22768) triggered Konus-Wind at T0=12541.046 s UT (03:29:01.046). The burst light curve shows several peaks with a total duration of ~7 s. The emission is seen up to ~1.5 MeV. As observed by Konus-Wind, the burst had a fluence of 4.61(-0.56,+0.72)x10^-6 erg/cm2, and a 64-ms peak energy flux, measured from T0+0.148 s, of 5.04(-2.18,+3.14)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 1.5 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with  alpha = -0.80(-0.26,+0.30), and Ep = 250(-47,+77) keV (chi2 = 52/60 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.25 (chi2 = 52/59 dof). The spectrum near the peak count rate (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 20 MeV range by the power law with exponential cutoff model with  alpha = -1.05(-0.29,+0.38), and Ep = 668(-304,+856) keV (chi2 = 23/19 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -1.80 (chi2 = 23/18 dof). The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180611_T12541/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.