TITLE:   GCN CIRCULAR
NUMBER:  14486
SUBJECT: GRB 130427A: Kanata/HOWPol optical imaging polarimetry
DATE:    13/04/28 10:21:20 GMT
FROM:    Koji Kawabata at HASC,Hiroshima U  <kawabtkj@hiroshima-u.ac.jp>

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.