Solar twins in M 67: evolutionary status and lithium abundance

¹ Departamento de Física Teórica e ExperimentalUniversidade Federal do Rio Grande do Norte, CEP: 59072-970 Natal, RN, Brazil
e-mail: mcastro@dfte.ufrn.br
² Istituto Nazionale di Astrofisica, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
³ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
⁴ Departamento de Astronomia do IAG/USP, Universidade de São Paulo, Rua do Matão 1226, São Paulo, 05508-900, SP, Brazil

Received: 24 May 2010
Accepted: 24 October 2010

Abstract

Aims. We determine the age and mass of the three best solar twin candidates in open cluster M 67 through lithium evolutionary models.

Methods. We computed a grid of evolutionary models with non-standard mixing at metallicity  [Fe/H]  = 0.01 with the Toulouse-Geneva evolution code for a range of stellar masses. We estimated the mass and age of 10 solar analogs belonging to the open cluster M 67. We made a detailed study of the three solar twins of the sample, YPB637, YPB1194, and YPB1787.

Results. We obtained a very accurate estimation of the mass of our solar analogs in M 67 by interpolating in the grid of evolutionary models. The three solar twins allowed us to estimate the age of the open cluster, which is  Gyr, which is better constrained than former estimates.

Conclusions. Our results show that the 3 solar twin candidates have one solar mass within the errors and that M 67 has a solar age within the errors, validating its use as a solar proxy. M 67 is an important cluster when searching for solar twins.