TITLE: GCN CIRCULAR NUMBER: 16173 SUBJECT: GRB 140423A: MITSuME Akeno Optical observation DATE: 14/04/25 14:28:40 GMT FROM: Taketoshi Yoshii at Tokyo Tech T. Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi, S. Kurita, Y.Ono , Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of GRB 140423A (E. Sonbas et al., GCN Circular #16142) 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 2014-04-23 12:38:42 UT (4.1h after the burst). We detected the previously reported optical afterglow of GRB140423A (D.Kuroda et al., GCN Circular #16160) in the Rc and Ic band. The measured magnitudes were listed below. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------------------------------- 19710 14:00:28 7740 20.49+/-0.23 19.83+/-0.15 19.72+/-0.22 31955 17:24:28 7560 >21.3 20.35+/-0.19 19.89+/-0.23 ------------------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used GSC2.3 catalog for flux calibration.