TITLE: GCN CIRCULAR NUMBER: 22504 SUBJECT: GROND observations of GRB 180316A DATE: 18/03/16 10:40:27 GMT FROM: Patricia Schady at MPE/Swift P. Schady and S. Steinmassl (both MPE) report: We observed the field of GRB 180316A (Swift trigger 814677; Melandri et al., GCN #22500) 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 06:46 UT on March 16, 1.8 hours after the GRB trigger. They were performed at an average seeing of 1.5" and at an average airmass of 1.5. We clearly detect the NIR/optical transient of GRB 180316A within the enhanced XRT position (Evans et al., GCN #22501), in agreement with the optical transient detected with MASTER (Lipunov et al., GCN #22502, #22503). Based on the first 4 minutes of exposure, we measure the following magnitudes (all in AB system): g' = 19.4 +/- 0.1 mag r' = 19.0 +/- 0.1 mag i' = 18.9 +/- 0.1 mag z' = 18.8 +/- 0.1 mag J = 18.2 +/- 0.1 mag H = 18.0 +/- 0.1 mag K = 17.8 +/- 0.2 mag Given magnitudes are calibrated against GROND zeropoints in g'r'i'z' and 2MASS field stars in JHK, and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.24 in the direction of the burst (Schlafly & Finkbeiner 2011). We acknowledge the excellent support from the TiO and the current observer at the 2.2m in La Silla, Sam Kim and Charlotte Brand.