GCN Circular 16939
D.A. Kann (TLS Tautenburg), T. Schweyer, J. F. Graham, J. Greiner (all MPE Garching) report on behalf of the GROND team: We observed the field of GRB 141022A (Swift trigger 616061; Vargas et al., GCN #16938) 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 01:39 UT on October 22nd, approximately 20 min after the GRB trigger. They were performed on a setting target at high airmass (~2.7) until reaching the pointing limit. Despite a crowed field we find only a single object in the 2.2" Swift-XRT enhanced error circle reported by Vargas et al., GCN #16938) at RA (J2000.0) = 16h 07m 28.82s DEC (J2000.0) = -72d 07' 29.6" (error of 0".5) but cannot ascertain variability in images centered 875 sec and 2095 sec after the trigger, and note the possibility of a chance coincidence given the density of objects in the field. We intended subsequent observations to determine variability. Based on a 16.5 min sequence of exposures, we estimate preliminary magnitudes and limits (all in AB system) of: g' = 23.6 +/- 0.2 mag r' = 22.2 +/- 0.1 mag i' = 21.6 +/- 0.1 mag z' = 22.0 +/- 0.2 mag J > 20.9 mag H > 20.3 mag K > 19.8 mag Given magnitudes are calibrated against GROND zeropoints and 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.1 mag in the direction of the burst (Schlegel et al. 1998).