TITLE: GCN CIRCULAR NUMBER: 6441 SUBJECT: GRB 070520A: Subaru Observations DATE: 07/05/21 16:14:41 GMT FROM: Nobuyuki Kawai at Tokyo Tech T. Hattori, K. Aoki (Subaru Telescope, NAOJ), and N. Kawai (Tokyo Tech) report on behalf of the Subaru GRB team: "We observed the field of GRB 070520A (Romano et al., GCN 6423) with FOCAS on the Subaru Telescope in the z'-band from 06:32(UT) to 07:27(UT) May 21 with a total exposure of 1920 sec (120s*16) under a non-photometric condition with occasional clouds. In the XRT error circle (Romano et al., GCN 6427), we find a possible afterglow candidate as a low-significance source (1.5 sigma) at RA=12:53:26.52, Dec=74:59:26.6 with a positional uncertainty of 0.4", and a rough estimation of the magnitude z' ~ 24. The image may be viewed at http://www.hp.phys.titech.ac.jp/nkawai/grb/070520A/ "