SCYON Abstract

Received on September 2 2008

Lithium depletion and the rotational history of exoplanet host stars

Authors	J. Bouvier
Affiliation	Laboratoire d'Astrophysique, Observatoire de Grenoble, CNRS, Université Joseph Fourier, B.P. 53, 38041 Grenoble, Cedex 9, France
Accepted by	Astronomy & Astrophysics
Contact	jbouvier@obs.ujf-grenoble.fr
URL
Links	ONC / NGC 2264 / NGC 2362 / NGC 2547 / Pleiades / M50 / M34 / M37 / Hyades

Abstract

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 develop 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 large 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 Li-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.