TITLE: GCN CIRCULAR NUMBER: 5094 SUBJECT: GRB060507: optical afterglow detection DATE: 06/05/09 13:17:15 GMT FROM: Christina Thoene at Niels Bohr Institute,DARK Cosmo Ctr Christina C. Thoene, Brian L. Jensen, Johan Fynbo (Dark Cosmology Centre), Jan-Erik Solheim (University of Oslo), and Erika Pakstiene (TFAI, University of Vilnius) report We observed the field of GRB060507 (GCN 5084) in the I-band with the NOT and ALFOSC on La Palma, starting at May 7th, UT 03:08:19 (1.13h after the burst) at high airmass. On the edge of the XRT revised error circle (99% confidence) (GCN 5087) we detect a new source at the position (J2000) RA = 05:59:50.52 Dec = +75:14:55.9 The preliminary I-band magnitude obtained from 3x300s stacked images with a mean time of 1.3h after the burst is I = 19.1 +- 0.1 (compared to four nearby USNO stars) 5x300 I-band images from May 9th show that the source is transient and therefore likely to be the afterglow of GRB060507 A finding chart is available at: http://www.astro.ku.dk/~brian_j/grb/grb060507.079/ [GCN OPS NOTE(10may06): Per author's request, the E.P. author was added.]