TITLE: GCN CIRCULAR NUMBER: 14742 SUBJECT: GRB 130603B: WHT optical afterglow candidate DATE: 13/06/03 22:53:37 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick), N.R. Tanvir, K. Wiersema (U. Leicester), O. Hartoog (Amsterdam), K. Kolle, J. Mendez (ING) and T. Kupfer (Nijmegan) report for a larger collaboration: We observed the location of GRB 130603B (Melandri et al. GCN 14735) with the William Herschel Telescope, beginning at 21:39 UT approximately 5.8 hours after the burst. In our z and r-band observations we identify a galaxy present in the SDSS DR9 observations of the field with a magnitude of r=20.94. In addition we identify a point-like source, offset approximately 1" to the SW of this source, with an approximate (+/- 1") position of; RA(J2000) 11 28 48.16 DEC(J2000) +17:04:18.0 This source is blended with the SDSS galaxy, but appears to be brighter. We suggest this is likely to be the optical afterglow of GRB 130603B."