TITLE: GCN CIRCULAR NUMBER: 17088 SUBJECT: GRB 141121A: MITSuME Akeno Optical observation DATE: 14/11/23 11:44:55 GMT FROM: Taketoshi Yoshii at Tokyo Tech S. Kurita, Y. Saito, Y. Tachibana, T. Yoshii, H. Ohuchi, Y. Yano, Y. Ono, T. Fujiwara, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 141121A (Lien et al., GCN Circular #17075) 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 2014-11-21 12:59:47 UT (~9 h after the burst). We detected the previously reported optical afterglow (Tanga et al., GCN Circular #17078) in the g',Rc and Ic band. The measured magnitudes are listed below. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ---------------------------------------------------------------------- 32947 17:07:07 12840 20.8 +/- 0.2 19.7 +/- 0.1 19.4 +/- 0.2 ---------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.