GCN Circular 10706
A.J. Levan (U. Warwick), A. Cucchiara (PSU), N.R. Tanvir (U. Leicester), D. Fox (PSU) report on behalf of a larger collaboration: "We obtained two epochs of observations of GRB 100420A (Baumgartner et al. GCN 10628) using Gemini-North/NIRI. Our first epoch consisted of 540s of observations in each of YJH and K and began at April 20 13:24 UT, approximately 8.2 hours after the burst. Our second epoch was obtained at April 22 14:27 ~57 hours after the burst. Within the refined XRT error circle we find a single object in our first epoch K-band observation. The object has a location of RA(J2000) 19:44:30.57 Dec(J2000) 55:46:10.0 with an error of 0.3" in each axis. It has a magnitude of K~21 in our first epoch observation, but has faded below our 3-sigma detection limit of K~22 in the second epoch. We therefore identify this source as the infrared afterglow of GRB 100420A. The source is not significantly detected in our J or H-band observations to preliminary limiting magnitudes of H>21.5, J>22.5 (3 sigma). However, because of the relative faintness of the K-band observations these limits are not constraining in terms of high-z and dust extinguished afterglow models"