TITLE: GCN CIRCULAR NUMBER: 15632 SUBJECT: GRB 131227A: GROND Upper Limits DATE: 13/12/29 17:07:39 GMT FROM: Alexander Kann at TLS Tautenburg D. A. Kann (MPE Garching), A. Nicuesa Guelbenzu (TLS Tautenburg) and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 131227A (Swift trigger 582184; Oates et al., GCN 15616) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at La Silla Observatory (Chile). Observations started at 02:10 UT on December 28th, around 21.4 hrs after the GRB trigger, and lasted for 2 hours. They were performed at an average seeing of 1".0 and at an average airmass of 2. At the position of the optical afterglow reported by Zheng et al. (GCN 15617) and Cucchiara et al. (priv. comm., see also GCN 15624) we do not detect any source down to 3-sigma AB limiting magnitudes of g' > 25.7, r' > 25.6, i' > 24.8, z' > 24.6, J > 21.8, H > 21.1, and K > 19.7. We do detect a compact source to the north-east, at RA (J2000) = 04:29:30.90 Dec. (J2000) = +28:53:00.3 with an uncertainty of 0".3 and AB magnitudes r' = 24.28 +/- 0.1, i' = 24.19 +/- 0.1, z' = 22.82 +/- 0.1, and J = 20.66 +/- 0.4. It is undetected to above-mentioned limits in the other filters. The relationship of this source to the afterglow is unclear. The given limits and magnitudes are derived based on calibrating the images against GROND zeropoints in g'r'i'z' and 2MASS field stars in JHK and are not corrected for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 1.02 mag in the direction of the burst (Schlegel et al. 1998).