TITLE: GCN CIRCULAR NUMBER: 22777 SUBJECT: GRB 180613A GROND observations DATE: 18/06/14 11:42:07 GMT FROM: Patricia Schady at MPE/Swift P. Schady, T. Schweyer, T.-W. Chen (all MPE Garching) and J. Bolmer (ESO Santiago) report: We observed the field of GRB 180613A (Swift trigger 840853; Tohuvavohu et al., GCN #22769) 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 23:30 UT on 2018-06-13, 7.9 hrs after the GRB trigger. They were performed at an average seeing of 1.5" and at an average airmass of 1.1. We do not detect the HAWKI source reported by Thoene et al. (GCN #2275). However, we note that the larger 4.9 arcsec uncertainty on the enhanced XRT position (Beardmore et al., GCN #22773) now includes two, brighter sources that are below the sensitivity of the DSS images. Source #1 lies at the SW edge of the enhanced XRT 90% error circle, at RA = 14:06:05.24 Dec = -43:04:21.6 with a preliminary magnitude r' = 23.1 +/- 0.1 mag. Source #2 lies at the NW edge of the enhanced XRT error circle, at RA = 14:06:05.24 Dec = -43:04:21.6 with r' = 22.9 +/- 0.1 mag. The above positions have an accuracy of 0.1" in both directions. Our g' band photometry is strongly affected by a nearby 5.6 mag star located SW of the GRB position, but source #1 is detected in all other GROND bands. Source #2 is detected in r', i' and z'. Our observations at the position of the XRT afterglow have preliminary 3 sigma upper limits of r' > 23.7 mag i' > 22.8 mag z' > 22.7 mag J > 21.5 mag H > 21.0 mag K > 20.4 mag All quoted magnitudes are in the AB system and are calibrated against GROND zeropoints and 2MASS field stars. They are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.08 in the direction of the burst (Schlafly & Finkbeiner 2011).