TITLE: GCN CIRCULAR NUMBER: 44671 SUBJECT: Konus-Wind detection of GRB 260518A DATE: 26/05/19 22:18:00 GMT FROM: Dmitry Svinkin at Ioffe Institute <dmitrysvinkin@gmail.com> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 260518A (AstroSat-CZTI detection: Harsha et al., GCN 44668) triggered Konus-Wind at T0=27873.529 s UT (07:44:33.529). The burst light curve shows a multipeaked structure which starts at ~T0-9 s and has a total duration of ~18 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260518_T27873/ As observed by Konus-Wind, the burst had the total fluence of 4.59(-0.38,+0.42)x10^-6 erg/cm2, and the 64-ms peak flux, measured from T0-0.016 s, of 2.35(-0.47,+0.48)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.11(-0.36,+0.42) and Ep = 213(-24,+31) keV (chi2 = 66/85 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.9 (chi2 = 66/84 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/44671. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...