Basic physical parameters of a selected sample of evolved stars

Silva, L. da; Girardi, L.; Pasquini, L.; Setiawan, J.; Lühe, O. von der; Medeiros, José Renan de; Hatzes, A.; Döllinger, M. P.; Weiss, A.

Basic physical parameters of a selected sample of evolved stars

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dc.contributor.author	Silva, L. da
dc.contributor.author	Girardi, L.
dc.contributor.author	Pasquini, L.
dc.contributor.author	Setiawan, J.
dc.contributor.author	Lühe, O. von der
dc.contributor.author	Medeiros, José Renan de
dc.contributor.author	Hatzes, A.
dc.contributor.author	Döllinger, M. P.
dc.contributor.author	Weiss, A.
dc.date.accessioned	2020-04-23T12:49:18Z
dc.date.available	2020-04-23T12:49:18Z
dc.date.issued	2006
dc.description.resumo	We present the detailed spectroscopic analysis of 72 evolved stars, which were previously studied for accurate radial velocity variations. Using one Hyades giant and another well studied star as the reference abundance, we determine the [Fe/H] for the whole sample. These metallicities, together with the Teff values and the absolute V-band magnitude derived from Hipparcos parallaxes, are used to estimate basic stellar parameters (ages, masses, radii, (B−V)0 and log g) using theoretical isochrones and a Bayesian estimation method. The (B−V)0 values so estimated turn out to be in excellent agreement (to within ∼0.05 mag) with the observed (B−V), confirming the reliability of the Teff−(B−V)0 relation used in the isochrones. On the other hand, the estimated log g values are typically 0.2 dex lower than those derived from spectroscopy; this effect has a negligible impact on [Fe/H] determinations. The estimated diameters θ have been compared with limb darkening-corrected ones measured with independent methods, finding an agreement better than 0.3 mas within the 1 <θ< 10 mas interval (or, alternatively, finding mean differences of just 6%). We derive the age-metallicity relation for the solar neighborhood; for the first time to our knowledge, such a relation has been derived from observations of field giants rather than from open clusters and field dwarfs and subdwarfs. The age-metallicity relation is characterized by close-to-solar metallicities for stars younger than ∼4 Gyr, and by a large [Fe/H] spread with a trend towards lower metallicities for higher ages. In disagreement with other studies, we find that the [Fe/H] dispersion of young stars (less than 1 Gyr) is comparable to the observational errors, indicating that stars in the solar neighbourhood are formed from interstellar matter of quite homogeneous chemical composition. The three giants of our sample which have been proposed to host planets are not metal rich; this result is at odds with those for main sequence stars. However, two of these stars have masses much larger than a solar mass so we may be sampling a different stellar population from most radial velocity searches for extrasolar planets. We also confirm the previous indication that the radial velocity variability tends to increase along the RGB, and in particular with the stellar radius.	pt_BR
dc.identifier.citation	MEDEIROS, José Renan de et al. Basic physical parameters of a selected sample of evolved stars. Astronomy & Astrophysics (Berlin), França, v. 458, n.in print, p. 609-623, 2006.ISSN 1432-0746 versão online. DOI https://doi.org/10.1051/0004-6361:20065105. Disponível em: https://www.aanda.org/articles/aa/abs/2006/41/aa5105-06/aa5105-06.html. Acesso em: 23 abr. 2020.	pt_BR
dc.identifier.doi	https://doi.org/10.1051/0004-6361:20065105
dc.identifier.issn	0004-6361 (print), 1432-0746 (online)
dc.identifier.uri	https://repositorio.ufrn.br/jspui/handle/123456789/28829
dc.language	en	pt_BR
dc.publisher	Astronomy & Astrophysics	pt_BR
dc.subject	Stars: fundamental parameters	pt_BR
dc.subject	Stars: evolution	pt_BR
dc.subject	Stars: oscillations	pt_BR
dc.subject	Hertzsprung-Russell (HR) and C-M diagrams	pt_BR
dc.subject	Stars: late-type	pt_BR
dc.subject	Stars: luminosity function, mass function	pt_BR
dc.title	Basic physical parameters of a selected sample of evolved stars	pt_BR
dc.type	article	pt_BR