TITLE: GCN CIRCULAR NUMBER: 14807 SUBJECT: GRB 130606A: GROND Detection of the Optical/NIR Afterglow DATE: 13/06/07 13:29:05 GMT FROM: Jonny Elliott at MPE/GROND P. Afonso (American River College), D. A. Kann, A. Nicuesa Guelbenzu (both TLS Tautenburg), T. Kruehler (DARK), J. Elliott, and J. Greiner (both MPE Garching) report on behalf of the GROND team: We observed the field of GRB 130606A (Swift trigger 557589; Ukwatta et al., GCN #14781) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). Observations started at 03:30 UT on 7th June 2013, 6.4 hours after the GRB trigger. They were performed at an average seeing of 1.1" and at an average airmass of 2.0. We detect the afterglow (Jelinek et al.; GCN #14782) at the position of Xu et al. (GCN #14783), and based on images taken at a mid-time of 05:00 UT, with total exposures of 7.66 minutes in g'r'i'z' and 8 minutes in JHK, we estimate preliminary magnitudes (all in AB) of g' > 24.3 mag, r' = 23.4 +/- 0.2 mag, i' = 21.4 +/- 0.1 mag, z' = 18.8 +/- 0.1 mag, J = 18.4 +/- 0.1 mag, H = 18.1 +/- 0.1 mag, and K = 17.8 +/- 0.2 mag. The spectral energy distribution is best fit with a small amount of LMC-like dust and a spectral slope of beta ~ 0.7. 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)=0.024 mag in the direction of the burst (Schlegel et al. 1998).