2001/05/25 by Albert A. Zijlstra
Physics and Astronomy · #astro-ph
published as Astrophys.Space Sci. 279 (2002) 171-182 · 12 pages, 3 figures. Invited review: Sakurai's object: What have we learned in the first five years?(Keele, UK). To be published in Astrophysics & Space Science
arxiv created 2001/05/25 · arxiv updated 2009/12/01
Five planetary nebulae are known to show hydrogen-poor material near the central star. In the case of A58, this gas was ejected following a late thermal pulse similar to Sakurai's Object. In this paper I will review these five objects. One of them, IRAS 18333-2357, may not be a true PN. I will show that there is a strong case for a relation to the [WC] stars and their relatives, the weak emission-line stars. The surface abundances of the [WC] stars are explained via diffuse overshoot into the helium layer. The hydrogen-poor PNe do not support this: their abundances indicate a change of abundance with depth in the helium layer. A short-lived phase of very high mass loss, the r-AGB, is indicated. Sakurai's Object may be at the start of such a phase, and may evolve to very low stellar temperatures.