TITLE: GCN CIRCULAR NUMBER: 9338 SUBJECT: GRB 090510: NOT afterglow confirmation DATE: 09/05/10 10:30:19 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst G. Olofsson, M. Ergon (Univ. Stockholm), D. Malesani, J.P.U. Fynbo (DARK/NBI), P. Jakobsson (Univ. Iceland), N.R. Tanvir, K. Wiersema (Univ. Leicester), A.J. Levan (Univ. Warwick), report on behalf of a larger collaboration: We observed the field of short Swift/Fermi GRB 090510 (Hoversten et al., GCN 9331; Ohno & Pelassa, GCN 9334; Guiriec et al., GCN 9336) with the Nordic Optical Telescope equipped with ALFOSC. Observations were carried out in twilight and at high airmass (~3). The candidate afterglow (Marshall & Hoversten, GCN 9332) is clearly detected in a stack of our images taken at a mean epoch May 10.215 UT (4.7 hr after the GRB). Calibrating against closeby USNO stars (R1 magnitudes), we get R ~ 21.2. Comparing this value with the magnitude reported by Marshall & Hoversten (GCN 9332) indicates fading, thus confirming that this object is the afterglow of GRB 090510. Astrometry of the field yields the following coordinates for the afterglow (0.4" error): RA(J2000) = 22:14:12.64 Dec(J2000) = -26:35:02.8 which is consistent with the UVOT position. We note the presence of a fainter source ~1" East of the afterglow. A finding chart is posted at the following URL: http://www.astro.ku.dk/~malesani/GRB/090510/090510_finder.png We acknowledge the observiers at the NOT for carrying out this difficult observation. [GCN OPS NOTE(10may09): The authors point out that there is a correction to the coordinates given above (see GCN Circ 9340).]