TITLE: GCN CIRCULAR NUMBER: 12988 SUBJECT: GRB 120224A: GROND detection of the afterglow candidate DATE: 12/02/27 01:33:33 GMT FROM: Jonny Elliott at MPE/GROND J. Elliott (MPE Garching), S. Klose (TLS Tautenburg) and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB120224A (Swift trigger 515976; Saxton et al., GCN #12980) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory (Chile). First observations started at 00:14 UT on 25 February 2012, 19.58 hrs after the GRB trigger. They were perfomed at an average seeing of 1".27 and at an average airmass of 1.4. After an exposure time of 4.72 min in g'r'i'z' and 8 min JHK, no source was detected. Second observations started at 00:48 UT on 26 February 2012, 1.84 days after the GRB trigger. They were performed at an average seeing of 0".96 and at an average airmass of 2.0. We find a single point source within the 1".8 refined Swift-XRT error circle reported by Osborne et al. (GCN #12981) at RA (J2000.0) = 02:43:46.15 = 40.94230 Dec. (J2000.0) = -17:45:42.0 = -17.76169 with an uncertainty of 0".5 in each coordinate. Based on total exposures of 36 min in JHK, we estimate preliminary magnitude (AB) of, J = 20.9 +/- 0.2 The given magnitude is calibrated against 2MASS field stars and is not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V)=0.04 in the direction of the burst (Schlegel et al. 1998).