GCN Circular 20070

T.Fujiwara, Y.Saito, Y. Tachibana, T. Yoshii, Y. Yano,
Y.Ono, S.Harita, Y.Muraki, K.Morita, T.Ozawa, K.Saisho,Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:

We searched for the optical counterpart of GRB 161017A (E. Troja et al., GCN
Circular #20064) 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 2016-10-17 17:52:42 UT (51 sec after the burst) and
we detected the optical counterpart in g', Rc and Ic band.
The measured magnitudes were listed as follows.

We obtained following results for the magnitudes.

T0+[sec]    MID-UT      T-EXP[sec]         g'              Rc                      Ic
-------------------------------------------------------------------------------------------------------
51            17:52:57        30          14.55 +/- 0.06        13.78 +/- 0.05      13.38 +/- 0.06
87            17:55:41        240         14.35 +/- 0.05        13.61 +/- 0.04      13.25 +/- 0.04
331          18:03:41        600         15.50 +/- 0.05        14.73 +/- 0.04      14.42 +/- 0.04
996          18:28:35        2100       16.58 +/- 0.05        15.89 +/- 0.05      15.63 +/- 0.04
3320        19:15:35        2040       16.76 +/- 0.06        16.03 +/- 0.05      15.77 +/- 0.05
-------------------------------------------------------------------------------------------------------

T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.