GCN Circular 14486
R. Itoh, K. Kawaguchi, Y. Moritani, K. Takaki, K. S. Kawabata, M. Ohno, H. Takahashi, Y. Tanaka, and M. Yoshida (Hiroshima Univ.) report on behalf of Kanata team: We performed a series of optical imaging polarimetry for the optical afterglow of GRB 130427A (Elenin et al., GCN 14450) from 3.87 hr through 10.04 hr after the Swift/BAT trigger (Maselli et al., GCN 14448) with HOWPol attached to the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Japan. Our quick-look analysis indicates that the R-band magnitude of the optical afterglow was 15.9 at the beginning of our observation, and then smoothly declined. Its decline rate between 3.87 hr and 10.04 hr can be approximated by a single power-low decay with an index -1.0. The polarization seems not so large (<~3%) in that period. Further analysis is ongoing.