TITLE: GCN CIRCULAR NUMBER: 17837 SUBJECT: Konus-Wind observation of GRB 150518A DATE: 15/05/21 11:15:33 GMT FROM: Dmitry Svinkin at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, report: At about 15 minutes before the MAXI/GSC trigger on GRB 150518A (Kawamuro, et al., GCN Circ. 17825; T0(MAXI)=21:42:14 UT) Konus-Wind detected in the waiting mode a burst of high X-ray/soft gamma-ray emission which had a duration of ~250 s. Taking in account the proximity of this burst to the MAXI/GSC trigger and consistency of the KW ecliptic latitude response with the position of GRB 150518A we suggest this burst is the main part of GRB 150518A. There is a hint of emission in the KW softest energy band (20-80 keV) around T0(MAXI). Due to a gap in the data during the main episode we cannot accurately estimate the burst energetics. The K-W light curve of this burst is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB150518A/