GCN Circular 30936

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).