TITLE: GCN CIRCULAR NUMBER: 6617 SUBJECT: GRB 070704: RTT150 optical observations DATE: 07/07/11 10:21:38 GMT FROM: Alexander Mescheryakov at IKI RAN A. Meshcheryakov, R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, Z. Tunca (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), I. Bikmaev, and N. Sakhibullin (KSU/AST) report: We observed the field of GRB 070704 (Sakamoto et al., GCN 6594) with Russian-Turkish 1.5-m telescope (RTT150, Bakyrlytepe,TUBITAK National Observatory, Turkey). The observations consisted of a series 30-second exposures in g',r',i' filters, until ~1h after the burst time we continue only r'-filter exposures. The first exposure in g' started at 20:15:13.9UT, i.e.556 s after the BAT trigger. The observations were finished ~1.5 hour after the burst time. In 30-second images as well as in combined images we do not detect any new object at the revised XRT position (Godet & Sakamoto, GCN 6598) down to following limiting magnitudes: Filter T_start(sec after trigger) Exp(s) Lim ---------------------------------------------------------------------------- g' 556 30 20.1 first 240 21.2 combined r' 641 30 20.1 first 1720 22.3 combined i' 721 30 20.3 first 180 21.3 combined This message may be cited. [GCN OPS NOTE(12jul07): Per author's request, IK was added to the author list, and the extra period after 'filter' in the 4th line was removed.]