TITLE: GCN CIRCULAR NUMBER: 6512 SUBJECT: GRB 070610: MITSuME OAO optical upper limit DATE: 07/06/12 07:07:28 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 070610 (Pagani et al. GCN 6489) with 50cm MITSuME telescope at Okayama Astrophysical Observatory from UT 12:27 to UT 12:41 on Jun 11 2007. We coadded 12 CCD frames for each band. Exposure time of each frame is 1 minute. We made flux calibration using USNO B1.0 catalg. No new source was found at the position of the afterglow candidate reported by A. de Ugarte Postigo (GCN 6501) and the XRT source reported by Pagani et al. (GCN 6490). Three sigma limiting magnitudes of our observation are listed below. ---------------------------------------------------- band mid-UT exp.time upper limit g' Jun 11 12:34 12 x 1 min. 18.7 mag Rc Jun 11 12:34 12 x 1 min. 19.0 mag Ic Jun 11 12:34 12 x 1 min. 19.0 mag ----------------------------------------------------