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Centro de Astrofísica da Universidade do Porto

Age and mass of solar twins constrained by lithium abundance

J. D. do Nascimento Jr., M. Castro, J. Meléndez, M. Bazot, S. Théado, G. F. Porto de Mello, J. R. de Medeiros

Abstract
Aims. We analyze the non-standard mixing history of the solar twins HIP 55459, HIP 79672, HIP 56948, HIP 73815, and HIP 100963, to determine as precisely as possible their mass and age.
Methods. We computed a grid of evolutionary models with non-standard mixing at several metallicities with the Toulouse-Geneva code for a range of stellar masses assuming an error bar of ±50K in Teff.We choose the evolutionary model that reproduces accurately the observed low lithium abundances observed in the solar twins.
Results. Our best-fit model for each solar twin provides a mass and age solution constrained by their Li content and Teff determination. HIP 56948 is the most likely solar-twin candidate at the present time and our analysis infers a mass of 0.994 ± 0.004 M⊙ and an age of 4.71 ± 1.39 Gyr.
Conclusions. Non-standard mixing is required to explain the low Li abundances observed in solar twins. Li depletion due to additional mixing in solar twins is strongly mass dependent. An accurate lithium abundance measurement and non-standard models provide more precise information about the age and mass more robustly than determined by classical methods alone.

Keywords
Stars: fundamental parameters - Stars: abundances - Stars: evolution - Stars: interiors

Notes
The models are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/... or via http://andromeda.dfte.ufrn.br.

Astronomy and Astrophysics
Volume 501, Page 687
July 2009

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