GCN Circular 20899

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME and OISTER collaboration:

We observed the field of GRB 170317A (LaPorte et al., GCNC 20885)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2017-03-17 10:14:19 UT (~28 min after
the burst). We detected the previously reported afterglow (LaPorte
et al., GCNC 20885; Mazaeva et al., GCNC 20886) in Rc and Ic bands.

Three sigma upper limit and photometric results of the OT are
listed below. We used GSC2.3 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'     Rc   Rc_err  Ic   Ic_err
------------------------------------------------------------------
0.06138    11:14:22    6120.0     >20.5  19.3 0.2     19.2 0.3"
------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]