TITLE: GCN CIRCULAR NUMBER: 19272 SUBJECT: GRB 160410A: GROND optical detection DATE: 16/04/10 06:34:19 GMT FROM: Robert Yates at MPE/Swift R Yates (MPE Garching) , T Kruehler (MPE Garching), J Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 160410A (Swift trigger 682269; Gibson et al., GCN #19271) 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 ESO La Silla Observatory (Chile). Observations started at 05:42 UT on 10-04-2016, 32mins after the GRB trigger. They were performed at an average seeing of 1.8" and at an average airmass of 2.7. We found a single point source within the 0.7" Swift-UVOT error circle reported by Gibson et al. (GCN #19271) at RA (J2000.0) = 10h 02m 44.37s DEC (J2000.0) = +03d 28' 42.4" with an uncertainty of 0.5" in each coordinate. Based on the first 4 min of total exposures in g'r'i'z' and JHK, we estimate preliminary magnitudes (all in AB system) of g' = 20.6 +/- 0.1 mag, r' = 20.5 +/- 0.1 mag, i' = 20.7 +/- 0.1 mag, z' = 20.5 +/- 0.2 mag, J > 20.0 mag, H > 19.6 mag, and K > 18.0 mag. Given magnitudes are calibrated against SDSS/2MASS 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)=0.0180 mag in the direction of the burst (Schlafly & Finkbeiner 2011).