TITLE: GCN CIRCULAR NUMBER: 9782 SUBJECT: GRB 090813: optical candidate from 1.23m CAHA telescope DATE: 09/08/13 05:01:48 GMT FROM: Javier Gorosabel at IAA-CSIC J. Gorosabel, V. Terron, M. Fernandez, P. Kubanek, M. Jelinek, A.J. Castro-Tirado (IAA-CSIC), on behalf of a larger collaboration, report; We have carried out I-band observations of the XRT position of GRB 090813 (GCN 9781) with the 1.23m telescope of Calar Alto. The observations started at 04:18 UT (437 s after the GRB trigger). We detect an object with a rough magnitude of I~17 coincident with the XRT position no present on the DSS. We propose that object as the optical afterglow of GRB 090813.