TITLE: GCN CIRCULAR NUMBER: 15107 SUBJECT: GRB 130816B: GROND afterglow candidate DATE: 13/08/17 08:19:40 GMT FROM: Karla Varela at MPE K. Varela (MPE Garching), S. Klose (TLS Tautenburg) and J. Greiner (both MPE Garching) report on behalf of the GROND team: We observed the field of GRB 130816B (Stamatikos et al., GCN #15099) simultaneously in g'r'i'z'JHKs 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 23:12 UT on 16 August 2013, 18.3 hours after the GRB trigger. They were performed at an average seeing of 1.6" and at and average airmass of 2.20. We find a source inside the 1.9" Swift-XRT error circle (Osborne et al., GCN #15102) at coordinates RA(J2000.0) = 11:20:03.96 DEC (J200.0) = -57:33:27.1 with an uncertainty of 0.5" in each coordinate. Based on the first 460 sec g'r'i'z and 480 sec JHK exposure, we estimate preliminary magnitudes (all in AB) of g' > 23.5 mag r' = 23.1 +/- 0.2 mag, i' = 22.5 +/- 0.2 mag, z' = 21.6 +/- 0.1 mag, J = 20.5 +/- 0.3 mag, H = 20.5 +/- 0.3 mag, K = 19.9 +/- 0.4 mag, calibrated against GROND zero points (griz) and 2MASS (JHK) and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.56 mag in the direction of the burst (Schlegel et al. 1998).