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Paper: Making Sense Out of Pulsating Pre-ELM and ELM White Dwarfs
Volume: 509, 20th European Workshop on White Dwarfs (EuroWD16)
Page: 347
Authors: Fontaine, G.; Istrate, A.; Gianninas, A.; Brassard, P.; Van Grootel, V.
Abstract: We present a unified view of pulsations in both pre-ELM and ELM white dwarfs within the framework of state-of-the-art binary evolution calculations that take into account the combined effects of diffusion and rotational mixing. We find that rotational mixing is able to maintain against settling a sufficient amount of helium in the envelope in order to fuel pulsations through He II-He III ionization on the pre-ELM branch of the evolutionary track in the spectroscopic HR diagram. By the time such a low-mass white dwarf enters the ZZ Ceti instability strip on the cooling branch, settling has taken over rotational mixing and produced a pure H envelope. Such a star then pulsates again, but, this time, as a DA white dwarf of the ZZ Ceti type.
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