TITLE: GCN CIRCULAR NUMBER: 20562 SUBJECT: GRB 170127A: GROND Upper limits DATE: 17/01/28 17:52:34 GMT FROM: Patricia Schady at MPE/Swift P. Schady, P. Wiseman and J. Greiner (all at MPE Garching) report on behalf of the GROND team: We observed the field of GRB 170127A (Swift trigger 735326; Markwardt et al., GCN #20538) 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 05:23 UT on 2017-01-27, 15 hrs after the GRB trigger. They were performed at high seeing that varied between 1.5” and 2" and at an average airmass of 1.4. In combined images with 36 min of total exposures in g’r'i'z' and 30 min in JHK at a mid-time of 05:40 UT on 2017-01-28, we do not detect a source within the Swift-XRT error circle reported by Evans et al. (GCN #20548) down to the following 3 sigma upper limits (all in AB system) g' > 24.0 mag r' > 23.7 mag i' > 23.1 mag z' > 23.0 mag J > 20.7 mag H > 20.3 mag K > 17.7 mag Given magnitudes are calibrated against GROND zeropoints and 2MASS field stars and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.06 in the direction of the burst (Schlafly & Finkbeiner 2011).