Age and mass of solar twins constrained by lithium abundance^*

¹ Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, CEP: 59072-970 Natal, RN, Brazil e-mail: dias@dfte.ufrn.br
² Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
³ Laboratoire d'Astrophysique de Toulouse et Tarbes - UMR 5572 - Université Paul Sabatier - CNRS, 14 Av. E. Belin, 31400 Toulouse, France
⁴ Universidade Federal do Rio de Janeiro, Observatório do Valongo, Ladeira do Pedro Antônio, 43, Rio de Janeiro, CEP: 20080-090, Brazil

Received: 24 February 2009
Accepted: 27 April 2009

Abstract

Aims. We analyze the non-standard mixing history of the solar twins HIP 55 459, HIP 79 672, HIP 56 948, HIP 73 815, and HIP 100 963, 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 ±50 K in T_eff. 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 T_eff determination. HIP 56 948 is the most likely solar-twin candidate at the present time and our analysis infers a mass of 0.994 ± 0.004  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.