Central stars of planetary nebulae: The white dwarf connection

Abstract

This paper is focused on the transition phase between central stars and white dwarfs, i.e. objects in the effective temperature range 100,000 - 200,000 K. We confine our review to hydrogen-deficient stars because the common H-rich objects are subject of the paper by Ziegler et al. in these proceedings. We address the claimed iron-deficiency in PG1159 stars and [WC] central stars. The discovery of new Ne VII and Ne VIII lines in PG1159 stars suggests that the identification of O VII and O VIII lines that are used for spectral classification of [WCE] stars is wrong. We then present evidence for two distinct post-AGB evolutionary sequences for H-deficient stars based on abundance analyses of the He-dominated O(He) stars and the hot DO white dwarf KPD0005+5106. Finally, we report on evidence for an H-deficient post-super AGB evolution sequence represented by the hottest known, carbon/oxygen-atmosphere white dwarf H1504+65 and the recently discovered carbon-atmosphere "hot DQ" white dwarfs.

Invited review, Proceedings IAU Symp. 283, Planetary Nebulae: An Eye to the Future, A. Manchado, L. Stanghellini, & D. Schoenberner, eds., Cambridge University Press

References in corpus (8)

• Rare White dwarf stars with carbon atmospheres
• Double white dwarf mergers and elemental surface abundances in extreme helium and R Coronae Borealis stars
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• Taking Advantage of the COS Time-Tag Capability: Observations of Pulsating Hot DQ White Dwarfs and Discovery of a New One
• The diffusion-induced nova scenario. CK Vul and PB 8 as possible observational counterparts
• Iron abundance in the prototype PG1159 star, GW Vir pulsator PG1159-035, and related objects
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Cited by in corpus (4)

• Magnetic fields in isolated and interacting white dwarfs
• On helium-dominated stellar evolution: the mysterious role of the O(He)-type stars
• Are planetary nebulae derived from multiple evolutionary scenarios?
• [WN] central stars of planetary nebulae