TITLE: GCN CIRCULAR NUMBER: 17903 SUBJECT: GRB 150518A: possible SN observations DATE: 15/06/06 15:19:15 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Pozanenko (IKI), E. Mazaeva (IKI), A. Sergeev (IRA NASU, IAKhNU), I. Reva (Fesenkov Astrophysical Institute), A. Volnova (IKI), E. Klunko (ISTP), I. Korobtsev (ISTP), report on behalf of larger GRB follow-up collaboration: We observed the field of the MAXI/GSC GRB 150518A (Kawamuro, et al., GCN 17825) with AZT-33IK telescope of Sayan observatory (Mondy), Zeiss-1000 (East) 1-m telescope of Tien Shan Astronomical Observatory and AZT-22 telescope of Maidanak observatory. Observations are continuing in R-filter. The SDSS J153648.25+161946.9 galaxy which coincides with the optical afterglow (Xu et al., GCN 17829) is detected in all observations. The light curve of the host galaxy+afterglow are suggesting re-brightening with a possible maximum brightness on June 2-5. We suggest that this re-brightening can be attributed to Supernova associated with GRB 150518A. Preliminary light curve of the possible SN+host can be found in http://grb.rssi.ru/GRB150518A/GRB150518A_lc.png Photometry of the host galaxy+SN at the possible maximum brightness are following Date UT start t-T0 Filter OT Err. Observatory (mid, days) 2015-06-02 17:43:30 14.8605 R 20.89 0.13 TSHAO 2015-06-03 20:33:20 15.8862 R 20.82 0.10 Maidanak 2015-06-05 18:11:19 17.8535 R 20.90 0.07 Maidanak Photometry is based on SDSS DR9 stars: SDSS9_id R(Lupton) J153646.11+161904.1 17.65 J153638.21+162002.8 18.41 J153637.55+162040.3 17.10 J153645.59+162055.5 16.35 The maximum brightness of a the possible Supernova is an agreement with the brightness predicted for the SN at redshift z = 0.256 (Xu et al., GCN 17832).