The rapid evolution of the born-again giant Sakurai's object

The extraordinarily rapid evolution of the born-again giant Sakurai's objec t following discovery in 1996 has been investigated. The evolution can be t raced both in a continued cooling of the stellar surface and dramatic chang es in chemical composition on a timescale of a mere few months. The abundan ce alterations are the results of the mixing and nuclear reactions which ha ve ensued due to the final He-shell flash which occurred during the descent along the white dwarf cooling track. The observed changes in the H and Li abundances can be explained by ingestion and burning of the H-rich envelope and Li-production through the Cameron-Fowler mechanism. The rapidly increa sing abundances of the light s-elements (including Sc) are consistent with current s-processing by neutrons released from the concomitantly produced C -13. However, the possibility that the s-elements have previously been synt hesized during the AGE-phase and only mixed to the surface in connection wi th the final He-shell flash in the pre-white dwarf cannot be convincingly r uled out either. Since Sakurai's object shows substantial abundance similar ities with the R CrB stars and has recently undergone R CrB-like visual fad ing events, the "birth" of an R CrB star may have been witnessed for the fi rst time ever. Sakurai's object thus lends strong support for the suggestio n that at least some of the R CrB stars have been formed through a final He -shell flash in a post-AGE star.