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 $\mathrm{3.8}{\mathrm{7}}_{-0.66}^{\mathrm{+}\mathrm{0.55}}$ 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.