TITLE: GCN CIRCULAR NUMBER: 18205 SUBJECT: GRB 150818A: possible SN rise in light curve of Mondy observations DATE: 15/08/27 16:54:50 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev (ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We continue observations of the Swift GRB 150818A (D'Elia et al., GCN 18152) with AZT-33IK telescope of Sayan observatory (Mondy). We imaged optical transient (Marshall et al., GCN 18155; McCauley et al., GCN 18161; Schulze et al., GCN 18164; Mazaeva et al., GCN 18175) in R-filter on Aug., 21, 22, 23, and 26. The optical transient is clearly visible in each epochs. Preliminary light curve of the optical transient can be found in http://grb.rssi.ru/GRB150818A/GRB150818A_R_lc.png (Photometry is based on USNO-B1.0 stars referenced in (Mazaeva et al., GCN 18175). One can suggest that steady re-brightening of the optical transient is related to a Supernova associated with nearby GRB 150818A (z = 0.282, Sanchez-Ramirez et al., GCN 18177). We encourage observation for spectroscopic SN-confirmation.