Benjamin J. Sharpee, Todd A. Thompson
We show that for a broad range of parameters, hierarchical triple star systems with similar masses are essentially unaffected by the Kozai-Lidov mechanism until the primary in the central binary evolves off the main sequence (MS) and begins mass loss. Subsequently, the primary becomes a white dwarf (WD) or a neutron star (NS) and may then be much less massive than the other components in the ternary, enabling the "eccentric Kozai mechanism:" the mutual inclination between the inner and outer binary can flip signs, driving the inner binary to very high eccentricity, and eventually tidal contact. Even distant binaries with initial semi-major axes larger then tens of AU can be strongly affected. We demonstrate this "Mass-loss Induced Eccentric Kozai" (MIEK) mechanism by considering an example system and explore the MIEK mechanism's dependence on the initial eccentricities and mutual inclination. For uniform distributions of eccentricity and cosine of the mutual inclination, we show that \sim 10% of systems interact tidally while the primary in on the MS. Approximately half of these are due to normal Kozai-Lidov oscillations, while the other half are due to the eccentric Kozai mechanism and may not have been captured by earlier quadrupole-order secular calculations. We then show that fully \sim 30% of systems interact tidally for the first time as the primary swells to AU scales, mostly as a result of the normal Kozai-Lidov mechanism. Finally, we show that \sim 2% of systems interact tidally for the first time after the primary sheds most of its mass and becomes a WD, mostly as a result of the MIEK mechanism. These findings motivate a more detailed study of mass loss in triple systems that includes observationally motivated distributions for the triple system's parameters. We conclude by discussing the implications of MIEK for the formation of close NS/WD-MS and NS/WD-NS/WD binaries.
View original:
http://arxiv.org/abs/1204.1053
No comments:
Post a Comment