GCN Circular 20585

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

We searched for the optical counterpart of GRB 1710202A (J. L. Racusin et
al., GCN Circular #20575) 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 2017-02-02 18:28:41 UT (39 sec after the burst).
We detected the optical counterpart (J. L. Racusin et al., GCN Circular #20575
) in g', Rc and Ic band.
The measured magnitudes were listed as follows.

T0+[sec]    MID-UT    T-EXP[sec]            g'                          Rc                          Ic    
-------------------------------------------------------------------------------------------------------
     54      18:28:56         30                >18.4                      >17.7                   >17.0
     92      18:29:34         30                >19.1                 17.01 +/- 0.12       17.08 +/- 0.25 
    131     18:30:13         30            17.61 +/- 0.13       16.38 +/- 0.09       15.89 +/- 0.12     
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.