TITLE:   GCN CIRCULAR
NUMBER:  25941
SUBJECT: LIGO/Virgo S190930t: J-GEM follow-up observation for Swift J221951-484240
DATE:    19/10/03 19:52:55 GMT
FROM:    Katsuhiro L. Murata at Nagoya U  <murata@u.phys.nagoya-u.ac.jp>

Kamei, Y.; Abe, F.; Tristram, P. J. (Nagoya U.); Murata, K. L. (Tokyo Institute of Technology); Onozato, H. (U. Hyogo); 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. (Oates et al., GCN Circ. 25901, 25939).

We observed one of the EM counterpart candidates of neutron star and black hole merger, Swift J221951-484240, using 61 cm Boller & Chivens telescope at Mt. John Observatory in New Zealand (B&C) and a three color imager Tripole5 (g, r, i). The brightness of the candidate on 2019-10-02 23:00:37 UTC (MJD 58758.490340) is
g~19.6
r~19.3
i~19.3 
in AB magnitude system compared with nearby stars with UCAC4 catalog (Zacharias et al. 2012).

We would like to thank observers for helping the observations.