TITLE: GCN CIRCULAR NUMBER: 14626 SUBJECT: GRB 130511A: Kanata/HOWPol optical observation DATE: 13/05/12 04:34:23 GMT FROM: Koji Kawabata at HASC,Hiroshima U K. Takaki, K. Kawaguchi, K. S. Kawabata, M. Ohno and M. Yoshida (Hiroshima Univ.) report on behalf of Kanata team: We performed optical observations of GRB 130511A (Krimm et al., GCN 14620) with HOWPol attached to the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Japan. The observation started at 11:32 UT on 2013 May 11 with imaging-polarimetry mode, followed by observation with imaging mode after 12:10 UT. We detected the optical afterglow of the GRB. Photometric results are shown below. We calibrated the Rc magnitude using USNO-B1.0 R2 magnitudes of nearby stars. Our result seems to be consistent with the brightness upper-limits reported in Xin et al. (GCN 14623) and Kuroda et al. (GCN 14625). The decline rate between these two epochs can be approximated by a single power-law with an index of -0.7. Mid time from Total Exp Filter Magnitude trigger (s) (s) ------------------------------------------------- 2571 300x2 Rc 20.0+-0.1 8768 300x2 Rc 21.0+-0.2 ------------------------------------------------- This message may be cited.