TITLE: GCN CIRCULAR NUMBER: 8049 SUBJECT: GRB 080727B: IR photometry DATE: 08/07/29 15:15:00 GMT FROM: Andrew Levan at U.of Leicester A.J. Levan (U. Warwick) and K. Wiersema (U. Leicester) report for a larger collaboration: We observed the location of GRB 080727B (Immler et al. GCN 8022) using UKIRT. The automatic observations begin at 08:27:13 UT, roughly 800 seconds after the burst. An initial set of K-band observations were acquired, followed by a shallower JHK sequence. At the location of the X-ray (Goad et al. GCN 8026) and optical/IR afterglows (D'Avanzo et al. GCN 8023; Li et al. GCN 8024) we clearly identify the fading afterglow of GRB080727B in all filters. The photometry, calibrated against several 2MASS stars within the field of view is shown below: =========================================== T_s T_s-T_b Band Mag err =========================================== 08:27:13 0.00959 K 13.952 0.03 08:31:38 0.01266 K 14.243 0.03 08:36:03 0.01573 K 14.392 0.03 08:50:08 0.02551 K 14.952 0.05 09:00:10 0.03248 K 15.276 0.05 09:10:09 0.03940 K 15.549 0.05 =========================================== 08:47:04 0.023389 H 16.144 0.06 08:58:06 0.031042 H 16.560 0.06 09:07:05 0.037280 H 16.775 0.08 ========================================== 08:43:13 0.02071 J 17.855 0.10 08:53:15 0.02767 J 18.300 0.10 09:03:16 0.03463 J 18.626 0.11 =========================================== *Data have not been corrected for the significant foreground extinciton The K-band is suggestive of a break occurring at t_b ~ 1600s, with pre- and post-break slopes of alpha_1 =0.84 and alpha_2 =1.26. The initial slope is significantly shallower than that suggested by the KAIT observations (Li et al GCN 8046), and implies either that the afterglow decay flatenned after those observations, or that the optical and IR were not tracking eachother in this case. We thank the staff of UKIRT for their rapid response to these alerts.