TITLE: GCN CIRCULAR NUMBER: 22624 SUBJECT: Konus-Wind observation of GRB 180404C DATE: 18/04/10 14:05:04 GMT FROM: Dmitry Svinkin at Ioffe Institute D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 180404C (CATET-GBM detection: Marrocchesi et al., GCN Circ. 22607; IPN triangulation: Hurley et al., GCN Circ. 22610) triggered Konus-Wind at T0=78131.929 s UT (21:42:11.929). The burst light curve shows a multi-peaked structure which starts at ~T0-88 s and has a total duration of ~200 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB180404_T78131/ As observed by Konus-Wind, the burst had a fluence of 1.33(-0.18,+0.19)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+2.672 s, of 2.11(-0.37,+0.37)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+116.736 s) is best fit in the 20 keV - 19 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.00(-0.10,+0.12), the high energy photon index beta = -2.40(-0.56,+0.24), the peak energy Ep = 342(-49,+58) keV (chi2 = 91/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+4.864 s) is best fit in the 20 keV - 19 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.58(-0.11,+0.13), the high energy photon index beta = -2.00(-0.12,+0.09), the peak energy Ep = 517(-71,+86) keV (chi2 = 86/94 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.