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Hydrogen-poor planetary nebulae

Albert A. Zijlstra
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Abstract

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.

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Albert A. Zijlstra. 2001-05-25. Hydrogen-poor planetary nebulae. https://arxiv.org/abs/astro-ph/0105448

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