Navegando por Autor "de Laverny, P."
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Artigo Lithium abundances and rotational behavior for bright giant stars(EDP Sciences, 2005-11-16) Lèbre, A.; de Laverny, P.; Nascimento Júnior, José Dias do; de Medeiros, J. R.Aims.We study the links possibly existing between the lithium content of bright giant stars and their rotational velocity. Methods.We performed a spectral analysis of 145 bright giant stars (luminosity class II) spanning the spectral range from F3 to K5. All these stars have homogeneous rotational velocity measurements available in the literature. Results.For all the stars of the sample, we provide consistent lithium abundances (ALi), effective temperatures (Teff), projected rotational velocity (), mean metallicity ([Fe/H]), stellar mass, and an indication of the stellar multiplicity. The gradual decrease in lithium abundance with Teff is confirmed for bright giant stars, and it points to a dilution factor that is at least as significant as in giant stars. From the F to K spectral types, the ALi spans at least three orders of magnitude, reflecting the effects of stellar mass and evolution on dilution. Conclusions.We find that the behavior of ALi as a function of in bright giant stars presents the same trend as is observed in giants and subgiants: stars with high ALi are moderate or fast rotators, while stars with low ALi show a wide range of valuesArtigo S1242: a lithium-rich subgiant star in the open cluster M 67(EDP Sciences, 2005-12-29) Martins, B. L. Canto; Lèbre, A.; de Laverny, P.; Melo, C. H. F.; Nascimento Júnior, José Dias do; de Medeiros, J. R.Aims.We report the serendipitous discovery of a lithium-rich subgiant star, S1242. This object is member of a large eccentricity spectroscopic binary system in the solar-age open cluster M 67. Methods.Using VLT/FLAMES-UVES observations and synthetic spectrum analysis, we derived for this star stellar parameters (temperature, gravity, metallicity and rotational velocity) and a surface Li abundance () larger than the higher abundance of M 67 stars near the turn-off. Results.The high Li abundance we found in S1242 points to an excess of lithium at the subgiant stage. We discuss two possible explanations for this unusually high Li content in this binary system: a preservation of the Li at the turn-off stage due to tidal effects, or an efficient dredge-up of Li, hidden below the convective zone by atomic diffusion occuring in the post turn-off stage