GCN Circular 25920
Murata, K. L. (Tokyo Institute of Technology); Sasada, M. (Hiroshima); Morokuma, T. (U. Tokyo) Utsumi, Y. (Stanford/SLAC) on behalf of J-GEM collaboration We report an optical follow-up observation for the electromagnetic counterpart candidate of the gravitational wave event S190930t (The LIGO Scientific Collaboration and the Virgo Collaboration, GCN Circ. 25876) reported by Stein et al. (GCN Circ. 25899). We observed one of the EM counterpart candidates of neutron star and black hole merger, AT2019rpj/ATLAS19wyn/ZTF19acbpsuf, using 50 cm MITSuME telescope at Akeno Observatory and a 3 color imager. The brightness of the candidate on 2019-10-01 at 18:44:02 UTC (MJD 58757.780578) is g'=19.8 +/- 0.5 Rc=19.3 +/- 0.3 Ic=19.1 +/- 0.3 in AB magnitude system by PSF photometry compared with the nearby star at (RA, Dec)=(339.82556, +31.50232) with Pan-STARRS DR1 catalog (Chambers et al. 2016).