摘要：Aims. We want to determine the lithium abundances of solar twin stars as
a function of stellar age to provide constraints for stellar evolutions models and to
investigate whether there is a connection between low Li abundance and the occurrence of
planets.
Methods. For a sample of 21 solar twins observed with the HARPS
spectrograph at high spectral resolution (R ≃ 115.000) and very high signal-to-noise ratio
(600 ≤
S/N ≤ 2400),
precise lithium abundances were obtained by spectral synthesis of the Li i 6707.8
Å line and compared to
stellar ages, masses, and metallicities determined from a spectroscopic analysis of the
same set of HARPS spectra.
Results. We show that for the large majority of the solar twins there is
a strong correlation between lithium abundance and stellar age. As the age increases from
1 to 9 Gyr, the Li abundance decreases by a factor of ~50. The relation agrees fairly well with
predictions from non-standard stellar evolution models of Li destruction at the bottom of
the upper convection zone. Two stars deviate from the relation by having Li abundances
enhanced by a factor of ~10,
which may be due to planet engulfment. On the other hand, we find no indication of a link
between planet hosting stars and enhanced lithium depletion.
关键词：stars: abundances;stars: evolution;planetary systems
