TITLE: GCN CIRCULAR NUMBER: 8983 SUBJECT: GRB 090313, GROND observations DATE: 09/03/13 10:34:51 GMT FROM: Sylvio Klose at TLS Tautenburg A. C. Updike (Clemson University), S. Klose (Tautenburg), C. Clemens and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 090313 (Swift trigger 346386; Mao et al. 2009, GCN 8980) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile). Observations started at 09:13 UT on March 13, 7 minutes after the GRB trigger. We confirm that the afterglow candidate reported by Chornock et al. (GCN 8979) is bright in all bands. We measure the following preliminary magnitudes at a mean time of about 10 minutes after the burst (Vega mags): J = 14.0 +/- 0.1 H = 13.1 +/- 0.1 K = 12.3 +/- 0.1 calibrated against 2MASS field stars. Astrometry gives RA, DEC (J2000) = 13:13:36.21, +08:05:49.2 (+/- 0.5 arcsec). As already noted by Chornock et al., the afterglow is close to a bright galaxy. These are preliminary data. Data reduction is in progress.