Tidal and rotational effects in the perturbations of hierarchical triple stellar systems^*

I. Numerical model and a test application for Algol

¹ Baja Astronomical Observatory of Bács-Kiskun County, 6500 Baja, Szegedi út, Pf. 766, Hungary e-mail: borko@alcyone.bajaobs.hu
² Eötvös University, Department of Astronomy, 1518 Budapest, Pf. 32, Hungary e-mail: E.Forgacs-Dajka@astro.elte.hu, rezso@general.elte.hu
³ Konkoly Observatory of HAS, 1525 Budapest, Pf. 67, Hungary

Received: 19 February 2004
Accepted: 29 June 2004

Abstract

A new numerical integrator has been developed for studying the orbital and spin evolution of hierarchical triple stellar systems. The code includes equilibrium tide approximations with arbitrary direction of rotational axes. The variation of the orbital elements (e.g. the inclination of the close – eclipsing – binary) and its observational consequences according to the distorted models with different mass-distributions of the stars, as well as with and without dissipation are studied in the case of the well-known eclipsing triple system Algol. We found that, in the absence of the tidal dissipation, the presence of the third star may cause sudden fluctuations in the orbital elements and the stellar rotation of the binary members even in the previously synchronized case, too. The dissipation can eliminate these fluctuations, nevertheless some variations which would produce observable effects in the same order which have been measured in several eclipsing binaries are also present.