[vsnet-grb-info 19042] GRB 170202A: MITSuME Akeno Optical Observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20585
SUBJECT: GRB 170202A: MITSuME Akeno Optical Observation
DATE:    17/02/03 00:47:37 GMT
FROM:    Yutaro Tachibana at Tokyo Tech  <tachibana at hp.phys.titech.ac.jp>

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.