TITLE: GCN CIRCULAR NUMBER: 30936 SUBJECT: Swift trigger 1078701: MITSuME Akeno optical upper limits DATE: 21/10/13 06:01:01 GMT FROM: Naohiro Ito at Tokyo Tech <n.ito@hp.phys.titech.ac.jp> N. Ito, R. Hosokawa, K. L. Murata, Y. Imai, Y. Takamatsu, M. Niwano, R. Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration: We observed the field of Swift/BAT trigger 1078701 (Bernardini et al., GCN #30929) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation with a series of 10 sec exposures started at 2021-10-10 10:43:22 (46 seconds after Swift trigger). We stacked the images with good conditions. We did not detect any uncatalogued sources within the BAT error region (Bernardini et al., GCN #30929). Also, we did not detect the possible optical counterpart reported by Mondy, CrAO, AbAO observations (N. Pankov et al., GCN #30932). We obtained the 5-sigma limits of the stacked images as follows. T0+[hour] MID-UT T-EXP[sec] 5-sigma limits ------------------------------------------------------------------------------------------------ 1.3 2021-10-10 12:00:19 540 g'>17.4, Rc>17.5, Ic>16.3 ------------------------------------------------------------------------------------------------ T0+ : Elapsed time after the burst T-EXP: Total Exposure time We used PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).