TITLE: GCN CIRCULAR NUMBER: 11210 SUBJECT: GRB 100902A: UKIRT JK Observation DATE: 10/09/05 07:10:32 GMT FROM: Myungshin Im at Seoul Nat U Myungshin Im, Changsu Choi, Hyunsung Jun, Eugene Kang (CEOU/Seoul National University), Y. Urata (NCU), P. Choi (Pomona College), and T. Sakamoto (NASA/GSFC), on behalf of a larger collaboration We observed GRB 100902A (Sakamoto et al. GCN 11181) in J and K filters using UKIRT. The observation started at Sept. 04, 14:24:39 UT or roughly 1.79 days after the BAT alert. The reduced images with non-optimal calibration frames do not show a clear sign of the afterglow candidate reported in Updike et al. (GCN 11209), although both the J and K images show a faint smudge at the reported location which may corresponds to the afterglow. The significance of the detection is only ~3 sigma (J ~ 20.8 mag, K ~ 19 mag in Vega), therefore it is difficult to draw a firm conclusion on detection or non-detection of the afterglow in our data. Further analysis of the UKIRT data is ongoing.