TITLE: GCN CIRCULAR NUMBER: 16713 SUBJECT: GRB140818B : GROND afterglow candidate DATE: 14/08/19 02:45:09 GMT FROM: Karla Varela at MPE F. Knust, K. Varela, and J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 140818B (Swift-60985; Vargas et al., GCN 16709) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla Observatory (Chile). Observations started at 23:43 UT on 2014-08-18, 5 hours after the GRB trigger. They were performed at an average seeing of 1.23" and at an average airmass of 1.2. Based on images with exposure times of 340s in g’r'i'z’ and 370s in JHKs, we detect a source inside the 1.9” error circle reported by Beardmore et al. (GCN 16712) at RA (J2000): 18h 04m 32.47s Dec (J2000): -01d 23’ 09.7" with an uncertainty of 0.5” and magnitudes g’ > 24.1 mag, r' = 22.1 +/- 0.1 mag, i' = 21.8 +/- 0.1 mag, z' = 21.4 +/- 0.1 mag. J > 20.9 mag, H > 20.7 mag, and K > 19.2 mag. The afterglow candidate reported by Aceituno et al. (GCN #16711) is also detected inside the 3.9” XRT error circle (GCN 16711) but not inside the 1.9” XRT error circle (GCN 16712) with magnitudes : r' = 22.4 +/- 0.1 mag, i' = 21.6 +/- 0.1 mag, z' = 20.9 +/- 0.1 mag. The given magnitudes are derived based on calibrating the images against the GROND zeropoints and 2MASS field stars are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.73 in the direction of the burst (Schlegel et al. 1998).