TITLE: GCN CIRCULAR NUMBER: 5652 SUBJECT: GRB 060729: An update on the late-time Swift observations DATE: 06/09/29 12:56:18 GMT FROM: Dirk Grupe at PSU/Swift-XRT D. Grupe (PSU) and Caryl Gronwall (PSU) report on behalf of the Swift team We report on an update of the Swift XRT and UVOT observations of GRB 060729 (Grupe et al., GCN 5365). The afterglow is still detectable in X-rays at a level of 1e-3 counts/s in the Swift XRT (5e-14 ergs/s/cm2). The late-time decay slope is 1.29+/-0.03. Assuming this decay slope continues, we expect the afterglow to be still detectable in the XRT until the end of December 2006. We plan to follow the afterglow as long as possible. Currently we are at day 61 after the burst, which is the longest period Swift has ever followed and detected an afterglow in X-rays. In the UVOT the afterglow was still visible in all 6 filters until 9 days after the burst. In UV W1 the afterglow was detectable until 2006-August-29 (31 days after the burst). we still obtain a 3.9 sigma detection at a level of 22.8+/-0.3 mag. We calculated the following late-time flux decay slopes in the 6 UVOT filters: V: 1.11+/-0.14 B: 0.98+/-0.07 U: 1.40+/-0.08 UVW1: 1.29+/-0.03 UVM2: 1.45+/-0.07 UVW2: 1.38+/-0.04 These values are slightly different than what has been reported earlier by Grupe (2006, GCN Circ. 5432). However, our new light curves contain more data than what was available earlier. Assuming the power law decay continues without a break in the optical, our extrapolation of the light curves show that the afterglow will be visible at the beginning of October with V=24.0 mag, B=23.4 mag, U=24.0 mag. At this level a detection of the afterglow is still feasible for a large southern telescope. We, therefore, encourage everybody again who has access to one of the large southern telescopes to follow this afterglow in V, B, and U in order to search for a break in the light curves. This circular is an official product of the Swift XRT Team.