TITLE: GCN CIRCULAR NUMBER: 19959 SUBJECT: GRB 160927A: GROND Observations DATE: 16/09/28 02:36:11 GMT FROM: Philip Wiseman at MPE/Swift P Wiseman (MPE Garching), J Bolmer (ESO Vitacura), and J Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 160927A (Swift trigger 713782; Gibson et al., GCN #19952) 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 23:26 UT on 27/09/2016, 5h 21m after the GRB trigger, and continued for ~1 hour, mostly during astronomical twilight. They were performed at an average seeing of 1.8" and at an average airmass of 2. Based on 22.4 min of total exposures around a mid-time of 5.58 hours after the trigger we marginally detect the source reported by Tkachenko et al. (GCN #19954) and D'Avanzo et al. (GCN#19956) in the GROND r’-band with an AB magnitude of: r' = 23.9 +/- 0.4 mag. The apparent fading since the RTT150 and TNG observations is convincing evidence for this source being the afterglow, and further suggests a steepening of the afterglow light-curve since the TNG observation. The given magnitude is calibrated against SDSS zeropoints and is not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.07 mag in the direction of the burst (Schlafly & Finkbeiner, 2011).