TITLE: GCN CIRCULAR NUMBER: 22056 SUBJECT: GROND observations of GRB 171027A DATE: 17/10/27 11:17:03 GMT FROM: Patricia Schady at MPE/Swift P. Schady (MPE) reports: Observations of the field of GRB 171027A (Swift trigger 783479; D'Avanzo et al., GCN #22053) were carried out simultaneously in g'r'i'z' 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 08:51 UT on 27-10-2017, 28.4 mins after the GRB trigger. They were performed during astronomical twilight, at an average seeing of 1.4" and at an average airmass of 1.4. Using a total exposure of 4.4 min, no source is detected within the 2.1" enhanced Swift/XRT error circle (Evans et al., GCN 22054) down to the following 3 sigma upper limits (all in AB): g' > 23.1 r' > 23.1 i' > 22.3 z' > 22.2 Given magnitudes are calibration against PanSTARRS and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.12 mag in the direction of the burst (Schlafly & Finkbeiner 2011). I acknowledge the excellent support provided by Angela Hempel in obtaining these data.