Brown dwarfs and the cataclysmic variable period minimum |
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| Authors: | U Kolb I Baraffe |
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| Institution: | Astronomy Group, University of Leicester, Leicester LE1 7RH; Ecole Normale Supérieure de Lyon, C.R.A.L. (UMR 5574 CNRS), F-69364 Lyon Cedex 07, France |
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| Abstract: | Using improved, up-to-date stellar input physics tested against observations of low-mass stars and brown dwarfs, we calculate the secular evolution of low-mass donor cataclysmic variables (CVs), including those that form with a brown-dwarf donor. Our models confirm the mismatch between the calculated minimum period ( P min70 min) and the observed short-period cut-off (80 min) in the CV period histogram. We find that tidal and rotational corrections applied to the one-dimensional stellar structure equations have no significant effect on the period minimum. Theoretical period distributions synthesized from our model sequences always show an accumulation of systems at the minimum period, a feature absent from the observed distribution. We suggest that non-magnetic CVs become unobservable as they are effectively trapped in permanent quiescence before they reach P min, and that small-number statistics may hide the period spike for magnetic CVs. |
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| Keywords: | accretion accretion discs methods: statistical binaries: close stars: evolution stars: low-mass brown dwarfs novae cataclysmic variables |
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