Tidal instability in exoplanetary systems' evolution

David Cébron (1) , Claire Moutou (2) , Michael Le Bars (1) , Patrice Le Gal (1) , R. Fares (3)

1 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre
2 LAM - Laboratoire d'Astrophysique de Marseille
3 LATT - Laboratoire Astrophysique de Toulouse-Tarbes

A new element is proposed to play a role in the evolution of extrasolar planetary systems: the tidal (or elliptical) instability. It comes from a parametric resonance and takes place in any rotating fluid whose streamlines are (even slightly) elliptically deformed. Based on theoretical, experimental and numerical works, we estimate the growth rate of the instability for hot-jupiter systems, when the rotation period of the star is known. We present the physical process, its application to stars, and preliminary results obtained on a few dozen systems, summarized in the form of a stability diagram. Most of the systems are trapped in the so-called "forbidden zone", where the instability cannot grow. In some systems, the tidal instability is able to grow, at short timescales compared to the system evolution. Implications are discussed in the framework of mis-aligned transiting systems, as the rotational axis of the star would be unstable in systems where this elliptical instability grows.

Mots clés: Tidal instability; misalignement; radius anomaly; extrasolar systems; dissipation

Domaines: Astrophysique stellaire et solaire [astro-ph.SR]; Astrophysique stellaire et solaire [astro-ph.SR]

David Cébron, Claire Moutou, Michael Le Bars, Patrice Le Gal, R. Fares. Tidal instability in exoplanetary systems' evolution. Detection and Dynamics of Transiting Exoplanets, Aug 2010, Haute Provence Observatory, Saint-Michel-l'Observatoire, France. ⟨hal-00558872⟩