TITLE: GCN CIRCULAR NUMBER: 10997 SUBJECT: GRB100725B: MITSuME optical upper limits DATE: 10/07/27 00:28:17 GMT FROM: Daisuke Kuroda at OAO/NAOJ D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 100725B (Baumgartner et al. GCNC 10983) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory. The observation started on 2010-07-25 14:05:46 UT (~2.7 h after the burst). We did not find any new point source within the XRT error circle (Goad et al., GCNC 10986) in all the three bands. Three sigma upper limits of the OT are listed below. We used SDSS catalog for flux calibration. T0+[day] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------ 0.13892 14:44:37 7620.0 >19.7 >19.3 >18.7 ------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]