TITLE: GCN CIRCULAR NUMBER: 1537 SUBJECT: XRF 020903: optical observation at Kyoto DATE: 02/09/06 11:26:27 GMT FROM: Taichi Kato at Kyoto U M. Uemura, R. Ishioka, T. Kato (Kyoto U) and H. Yamaoka (Kyushu U) report on behalf of VSNET-grb collaboration: "We have performed a full analysis of unfiltered CCD images of XRF 020903 (GCN 1530) taken with 25-cm telescope at Kyoto. The observation starts on Sept. 3.595 UT, i.e., 4.2 hours after the flash detection. We imaged the central region of initial XWM error circle, so the coverage of WXM+SXC error box is as rather small as 10%. Our field of view is described in: http://www.rc.kyushu-u.ac.jp/~yamaoka/XRF020903/FOV.gif . It contains the central region of the cluster Abell 2487. A stacked image (30s x 60 exposures), whose limiting magnitude is R ~ 17.5 compared with USNO-A2.0 r mag, revealed no definite new source within our image compared with DSS 2 red image. (Note: XRF 020903 occurred at a location very close to GRB 990527 (GCN 347). The WXM+SXC error box of XRF 020903, however, does not overlap the IPN error box of GRB 990527, as shown in FOV.gif mentioned above.)" This message may be cited.