White dwarf + red dwarf binary systems and the period gap of cataclysmic variables |
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| Authors: | N F Vojkhanskaja |
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| Institution: | (1) Special Astrophysical Observatory, Russian Academy of Sciences, Russia |
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| Abstract: | Cataclysmic variables (CV) and pre-cataclysmic binaries (PCB) are discussed. The main difference between them (accretion or
its absence) is shown to be a consequence of the evolutionary process and the properties of their progenitors. Both types
of system have a bimodal distribution of their periods, but the extrema are in counterphase. Luminosity-effective temperature
diagrams for the primary components are used to show that both systems have approximately the same age, which conflicts with
the notion of PCBs as precursors of CVs. Calculations of the maximum distance between components for which the system remains
stable show that CVs have passed this limit, while PCBs maintain their stability during this evolution. It is suggested that,
after ejecting a common shell, future CVs immediately become semi-detached systems. It this is so, then there must be cataclysmic
variables which are the central stars of planetary nebulae.
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Translated from Astrofizika, Vol. 50, No. 3, pp. 427–439 (August 2007). |
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| Keywords: | stars cataclysmic variables stability of systems period gap |
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