TITLE: GCN CIRCULAR NUMBER: 14193 SUBJECT: GRB 130131B: MITSuME Akeno Optical upper limits DATE: 13/02/10 13:58:00 GMT FROM: Yoichi Yatsu at Tokyo Tech. M. Hayashi, T. Yoshii, R. Usui, Y.Aoki, S. Kurita, Y. Saito, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed GRB 130131B (Siegel et al., GCNC 14159) 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 2013-01-31 19:10:57 UT (~49 sec after the burst). And we could not find any new point source within the XRT error circle in all the three bands. The results of photometry (3 sigma upper limits) are listed below. The photon flux were calibrated against GSC2.3 catalog. T0+[sec] MID-UT T-EXP[sec] g' Rc Ic ------------------------------------------------------------------------------------------- 70 19:12:07 60 >16.4 >16.4 >16.2 178 19:13:55 240 >17.4 >17.6 >17.4 1183 19:30:40 1320 >18.6 >19.0 >18.9 2769 19:57:06 4200 >19.1 >19.6 >19.5 ------------------------------------------------------------------------------------------- T0+ : Elapsed time after the burst [sec] T-EXP: Total Exposure time [sec]