TITLE: GCN CIRCULAR NUMBER: 6552 SUBJECT: GRB070616: Optical Observation by MITSuME Okayama DATE: 07/06/18 05:05:26 GMT FROM: Michitoshi Yoshida at Okayama Astrophysical Obs M. Yoshida, K. Yanagisawa, Y. Shimizu, S. Nagayama (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We performed optical imaging observation (g', Rc, and Ic) of the field of GRB 070616 (Starling et al. GCN 6542) with 50cm MITSuME telescope at Okayama Astrophysical Observatory from UT 18:04:40 (1h 35m after burst) to UT 18:10:30 on June 16 2007. We coadded 5 CCD frames for each band. Exposure time of each frame is 1 minute. We made flux calibration using USNO B1.0 catalg. We could not identify new source at the position of the afterglow candidate reported by Fatkhullin et al. (GCN 6547) and Ugarte Postigo (GCN 6548). Three sigma limiting magnitudes of our observation are listed below. ---------------------------------------------------- band mid-UT (2007) exp.time upper limit g' June 16 18:07:35 5 x 1 min. 19.5 mag Rc June 16 18:07:35 5 x 1 min. 18.9 mag Ic June 16 18:07:35 5 x 1 min. 18.4 mag ----------------------------------------------------