TITLE: GCN CIRCULAR NUMBER: 13915 SUBJECT: GRB 121028A: MITSuME Okayama Optical upper limits DATE: 12/10/28 13:05:18 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 121028A (Starling et al., GCNC 13913) 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 2012-10-28 09:15:55 UT (~4.2 h after the burst). We did not find any new point source within the XRT circle (Starling et al., GCNC 13913) in all the three bands. Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration. T0+[day] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------ 0.21623 10:15:53 6360.0 >19.7 >19.4 >18.7 ------------------------------------------------------ T0+ : Elapsed time after the burst [day] T-EXP: Total Exposure time [sec]