TITLE: GCN CIRCULAR NUMBER: 22554 SUBJECT: Konus-Wind observation of GRB 180318A DATE: 18/03/27 16:06:20 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 180318A (IPN Triangulation: Hurley et al., GCN 22522) triggered Konus-Wind at T0=84002.795 s UT (23:20:02.795). The burst light curve shows two emission episodes with multipeaked structure, which start at ~T0-53 s and have a total duration of ~280.0 s. The main episode lasts from ~T0-53 s to ~T0+30 s, the second episode lasts from ~T0+150 s to ~T0+200 s. The emission is seen up to 1.2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180318_T84002/ As observed by Konus-Wind, the burst had a fluence of 1.13(-0.24,+0.23)x10^-4 erg/cm2, and a 64-ms peak energy flux, measured from T0+18.560 s, of 4.89(-1.04,+1.11)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+205.056 s) is best fit in the 20 keV - 1.2 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.89(-0.24,+0.31), the high energy photon index beta = -2.12(-0.48,+0.18), the peak energy Ep = 195(-45,+69) keV, chi2 = 83/59 dof. The spectrum near the maximum count rate (measured from T0+16.640 to T0+24.832 s) is best fit in the 20 keV - 1.2 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with  alpha = -0.98(-0.19,+0.22) and Ep = 251(-40,+63) keV (chi2 = 63/60 dof). Fitting by the GRB (Band) model yields the same alpha and Ep, and  beta < -2.13 (chi2 = 62/59 dof) All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.