TITLE: GCN CIRCULAR NUMBER: 16099 SUBJECT: GRB 140413A: GROND afterglow candidate DATE: 14/04/13 01:37:26 GMT FROM: Ana Nicuesa at TLS Tautenburg K. Varela, C. Delvaux (both MPE Garching), A. Nicuesa Guelbenzu (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 140413A (Swift trigger 595616; D'Elia et al., GCN #16098) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at La Silla Observatory (Chile). Observations started at 00:13 UT on 13 April 2014, less than 5 min after the GRB trigger, and are continuing. They are performed at a mean airmass of 1.9 and a mean seeing of 0.9". We find a single point source within the 5.8" Swift/XRT error circle at coordinates RA(J2000) = 04:21:49.23 Dec(J2000) = -51:10:58.0. At a midtime of 00:17 UT we measure the following preliminary AB magnitudes: r' = 20.2 +/- 0.1, i' = 19.6 +/- 0.1, z' = 19.3 +/- 0.1. The source is also visible in g. At present we cannot decide if the source is fading. Data processing is still ongoing, observations are continuing. Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.02 mag in the direction of the burst (Schlegel et al. 1998).