HST observations of Sakurai's Object (V4334 SGR) and related stars

We describe our ongoing program of HST observations of Sakurai's Object (V4334 Sgr). Direct WFPC2 imaging from August 1996 through August 2000 reveals no transient features (such as light echoes), and documents the decline of the star to below 24th visual magnitude in 2000. The surrounding planetary nebula has shown no changes from 1996 through 2000. There are no obvious peculiar features (such as blobs or knots) in the immediate vicinity of the star. We also have in place a target-of-opportunity program to obtain UV spectra with HST in the event that the star begins to retrace its evolution back to high surface temperature. We also present older HST FOC imaging of V605 Aql. The central object is a resolved nebula that emits in [O III] (but not in hydrogen), whose 0″.6 diameter is consistent with a dust cloud ejected during the 1919 outburst. The central star itself is not seen due to its being embedded in the nebula. Several other central stars (including H 3-75, IC 2120, and Abell 14) have late-type nuclei and no evidence for hot companions. They may be further candidates for 'born-again' red-giant nuclei.