Tidal and Rotational Effects in the Evolution of Hierarchical Triple Stellar Systems

Abstract

A new numerical integrator was developed by the author for studying together the orbital and spin evolution of hierarchical triple stellar systems. The stars are considered as liquid, viscous bodies. The initial orientation of the axis of rotation of each component can be arbitrary. The angular velocity of the rotation can differ from the Keplerian angular velocity. The equations of the orbital motion and the (Eulerian) equations of the star rotations are integrated simultaneously. The dynamical tides are treated as a force term calculated as the divergence of the viscous stress tensor (see eg. Kopal, 1978). Only the first order terms are integrated. For the more distant third companion only a mass—point model is applied. This means the effect of the third body is calculated only as a point mass—point mass interaction. The numeric integrator is a seventh order Runge-Kutte-Nyström one (Fehlberg, 1974). Regularization is not applied.