Lithium depletion and the rotational history of exoplanet host stars

Jerome Bouvier (1)

1 LAOG - Laboratoire d'Astrophysique de Grenoble

Israelian et al. (2004) reported that exoplanet host stars are lithium depleted compared to solar-type stars without detected massive planets, a result recently confirmed by Gonzalez (2008). We investigate whether enhanced lithium depletion in exoplanet host stars may result from their rotational history. We have developed rotational evolution models for slow and fast solar-type rotators from the pre-main sequence (PMS) to the age of the Sun and compare them to the distribution of rotational periods observed for solar-type stars between 1 Myr and 5 Gyr. We show that slow rotators develop a high degree of differential rotation between the radiative core and the convective envelope, while fast rotators evolve with little core-envelope decoupling. We suggest that strong differential rotation at the base of the convective envelope is responsible for enhanced lithium depletion in slow rotators. We conclude that lithium-depleted exoplanet host stars were slow rotators on the zero-age main sequence (ZAMS) and argue that slow rotation results from a long lasting star-disk interaction during the PMS. Altogether, this suggests that long-lived disks (> 5 Myr) may be a necessary condition for massive planet formation/migration.

Mots clés: Stars: planetary systems : formation; Stars : rotation; Stars : abundances; Stars : pre-main sequence; Accretion; accretion disks; Hydrodynamics

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]

Jerome Bouvier. Lithium depletion and the rotational history of exoplanet host stars. Astronomy and Astrophysics - A&A, 2008, pp.0. ⟨hal-00315484v4⟩