TITLE: GCN CIRCULAR NUMBER: 7863 SUBJECT: GRB080605: optical observation with the MITSuME-OAO telescope DATE: 08/06/09 00:24:33 GMT FROM: Michitoshi Yoshida at Okayama Astrophysical Obs M. Yoshida, K. Yanagisawa, D. Kuroda, Y. Shimizu, S. Nagayama, H. Toda (OAO, NAOJ) and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We performed optical imaging observation (Rc, and Ic) of the field of GRB 080605 (Sbarufatti et al., GCN 7828) with 50cm MITSuME telescope at Okayama Astrophysical Observatory June 6 2008 UT. We detected a point source at the UVOT position of the optical afterglow (Kuin et al., GCN 7844). Differential photometry was made using a USNO B1.0 star, USNO-ID 0940-0289655 (Kann et al., GCN 7845). The Ic-band magnitude of the source was almost constant from T-T0 = 0.516 to 0.756. The source is about 1.5 magnitude fainter in Rc-band than in Ic-band. These results are consistent with other reports (Kann et al., GCN 7845, Rumyantsev et al., GCN 7857). MITSuME observation start: 2008-06-06 11:35:11 UT mid-UT T-T0(days) exp-T Ic (2008-06-06) --------------------------------------------------- 12:11:27 0.516314 60 min 19.03 +/- 0.38 12:48:05 0.541753 60 min 19.00 +/- 0.29 14:00:54 0.592315 60 min 18.85 +/- 0.18 15:15:44 0.644288 60 min 19.03 +/- 0.22 16:30:50 0.696429 60 min 18.82 +/- 0.21 17:56:24 0.755856 80 min 18.87 +/- 0.30 --------------------------------------------------- mid-UT (2008-06-06) T-T0(days) ext-T Rc --------------------------------------------------- 15:52:20 0.669745 120 min 20.58 +/- 0.32 ---------------------------------------------------