TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4053 SUBJECT: GRB 051001: AAT infra-red observations DATE: 05/10/02 01:02:32 GMT FROM: Evert Rol at U.Leicester E. Rol (U. of Leicester), A. Levan, N. Tanvir (U. of Hertfordshire), report on behalf of a larger collaboration: We have observed the field of GRB 051001 (Moretti, GCN 4051) with the IRIS2 instrument on the Anglo-Australian Telescope. Two epochs of observations were performed in each of the ZJHKs bands, roughly 2 hours and 6 hours after the trigger, respectively. Our observations covered the entire BAT error box, albeit with a small section (<5%) on the edge of the FOV. Comparison between the two epochs shows no variable sources. Inside the XRT error circle, one source is visible, which appears to be extended. Its location is, calibrated to the 2MASS: RA 23:23:49.04 (J2000) Dec -31:31:18.8 (J2000) with an estimated error of 0.16" in each coordinate. Magnitude estimates for the first epoch, calibrated with respect to the 2MASS, are as follows: filter mid-time exposure magnitude limiting after trigger time of extended magnitude (hours) (minutes) source (3 sigma) Ks 1.40 20 18.7 (0.1) 20.3 H 1.85 20 20.0 (0.1) 20.7 J 2.36 10 20.9 (0.3) 20.7 The first epoch Ks image can be seen at http://www.star.le.ac.uk/~er45/grb051001/