TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4146 SUBJECT: GRB051021b: Magellan IR Imaging DATE: 05/10/23 05:45:47 GMT FROM: Josh Bloom at UC Berkeley D. L. Kaplan (MIT), H-W. Chen (Chicago), J. S. Bloom (UCB), J. X. Prochaska (UCO LIck) report on behalf of a large collaboration: "We obtained deep K-band imaging of the field of GRB 051021b (GCN 4135) with PANIC on the Magellan Baade Telescope starting at 08:42:56 October 22, 2005 UTC. We identify 4 sources within the XRT error circle (GCN 4128): 08:24:11.803 -45:32:30.79 J2000 08:24:11.598 -45:32:31.93 J2000 08:24:11.622 -45:32:33.70 J2000 08:24:11.724 -45:32:34.20 J2000 The 1 sigma uncertainty relative to 2MASS is 300 mas. As all of these sources are significantly fainter than the 2MASS detection limit we cannot identify an obvious afterglow candidate." This message may be cited.