TITLE: GCN CIRCULAR NUMBER: 9037 SUBJECT: GRB 090323: RTT150 optical observations DATE: 09/03/25 12:22:37 GMT FROM: Rodion Burenin at IKI, Moscow R. Burenin, A. Tkachenko, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), I. Bikmaev, N. Sakhibullin (KSU/AST) report: The optical afterglow of GRB 090323 (Updike et al., GCN 9026, Cenko et al., GCN 9027) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey). We obtained 6x600s exposures in sdss-r filter, centered at March 25, 01:30 UT, i.e. 2.059 days after the burst. The afterglow is detected in all frames. Using the same calibration star as it was used by Kann et al. (GCN 9033), we esimate the magnitude of the OT as R=20.85+-0.04. During our observations we also marginally detected gradual decline of the afterglow brightness at a rate of approximately 0.3 mag/hour, which is steeper than that assumed by the comparison with the data obtained by Perley et al. (GCN 9036). Our light curve and finding chart can be found at: http://hea.iki.rssi.ru/grb/090323/indexeng.html