TITLE:   GCN CIRCULAR
NUMBER:  23968
SUBJECT: GRB190311A: MITSuME Akeno optical observation
DATE:    19/03/15 12:11:13 GMT
FROM:    Kota Iida at Tokyo Inst. of Tech.  <kota0722iida@gmail.com>

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

We searched for the optical counterpart of GRB 190311A (Troja et
al., GCN
Circular #23946) with the optical three color (g', Rc, and Ic) CCD cameras
attached to the MITSuME 50cm telescope of Akeno Observatory, Yamanashi,
Japan.

The observation started on 14:24:43.64 UT which corresponds to
70 sec after the trigger.
We detected the point source at the position consistent with the
afterglow detected previously (Troja et al. GCN #23946; Pozanenko et
al. GCN #23947; Zhu et al. GCN #23948; Gorbovskoy et al. GCN #23949,
Belkin et al. GCN #23951).
The measured magnitudes are listed as follows.

T0+[sec]    MID-UT      T-EXP[sec]        g'       Rc        Ic
-------------------------------------------------------------------------------------------------------
~70      14:24:46.22          540              18.9+/-0.2
18.6+/-0.2     18.2+/-0.2
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.
The magnitudes are expressed in the Vega system.