[vsnet-grb-info 21246] GRB 181011A: MITSuME Akeno and Okayama optical upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23345
SUBJECT: GRB 181011A: MITSuME Akeno and Okayama optical upper limits
DATE:    18/10/17 10:02:24 GMT
FROM:    Adachi Ryo at Tokyo Institute of Tech  <adachi at hp.phys.titech.ac.jp>

R. Adachi, R. Itoh, K. L. Murata, Y. Tachibana, K. Morita,
K. Shiraishi, K. Iida, M. Oeda, M. Niwano,
Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We performed tiling observation for error region of GRB 181011A
(Kawakubo et al., GCN Circular #23327)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the two MITSuME 50cm telescopes at  Akeno Observatory
and Okayama Astrophysical Observatory, in Japan.

The observation started on 2018-10-12 13:51:34 UT.
Our tiling observation covers about 90% of MAXI error region.
We did not find any point source at the position of the
MAXI error box (Kawakubo et al., GCN Circular #23327)
in all three bands.
Unfortunately, thin cloud were passing during the observation therefore
we could not obtain uniform exposure for each data set between tiling.
Finally we obtained following 5-sigma upper limits for the magnitudes

35% region: g' > 18.0, Rc > 17.7, Ic > 17.0
40% region: g' > 16.5, Rc > 16.2, Ic > 15.7
15% region: g' > 15.0, Rc > 14.7, Ic > 14.2

We used UCAC-4 catalog for flux calibration.