TITLE: GCN CIRCULAR NUMBER: 17215 SUBJECT: GRB 141220A: MITSuME Akeno upper limits DATE: 14/12/22 07:06:48 GMT FROM: Taketoshi Yoshii at Tokyo Tech Y. Yano, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, S. Kurita, Y. Ono, T. Fujiwara, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 141220A (J. R. Cummings et al., GCN Circular #17196) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan. The observation started on 2014-12-20 15:16:22 UT (~9.2 h after the burst). We did not find any new point source within the refined XRT error circle (B. P. Gompertz., GCN Circular #17203) in all the three bands. The measured magnitudes are listed below. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ----------------------------------------------------------------------------- 36707 18:07:29 8460 >21.4 >20.8 >20.4 ----------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.