The age of the Galactic thin disk from Th/Eu nucleocosmochronology I. Determination of [Th/Eu] abundance ratios

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dc.creatordel Peloso, E. F.
dc.creatorda Silva, L.
dc.creatorde Mello, G. F. Porto
dc.date2004-11-25
dc.date2005-02-21
dc.date.accessioned2026-07-07T02:16:02Z
dc.date.available2026-07-07T02:16:02Z
dc.descriptionThe purpose of this work is to resume investigation of Galactic thin disk dating using nucleocosmochronology with Th/Eu stellar abundance ratios, a theme absent from the literature since 1990. A stellar sample of 20 disk dwarfs/subgiants of F5 to G8 spectral types with -0.8 <= [Fe/H] <= +0.3 was selected. In stars with such spectral types and luminosity classes, spectral synthesis techniques must be employed if we wish to achieve acceptably accurate results. A homogeneous, self-consistent set of atmospheric parameters was determined. Effective temperatures were determined from photometric calibrations and H-alpha profile fitting; surface gravities were obtained from Teff, stellar masses and luminosities; microturbulence velocities and metallicities were obtained from detailed, differential spectroscopic analysis, relative to the Sun, using equivalent widths of Fe I and Fe II lines. Chemical abundances of the elements that contaminate the Th and Eu spectral regions (Ti, V, Cr, Mn, Co, Ni, Ce, Nd, and Sm) were determined through spectroscopic analysis. Abundance uncertainties were thoroughly scrutinised, their average value - (0.10 +/- 0.02) dex - being found to be satisfactorily low. Eu and Th abundances were determined by spectral synthesis of one Eu II line (4129.72 A) and one Th II line (4019.13 A), taking into account the detailed hyperfine structures of contaminating Co lines, as well as the hyperfine structure and isotope shift of the Eu line. Comparison of our abundances with literature data shows that our results exhibit a similar behaviour, but a considerably lower scatter (36% lower for Eu, and 61% lower for Th). The [Th/Eu] abundance ratios thus obtained were used, in the second paper of this series, to determine the age of the Galactic disk.
dc.description27 pages, 22 Postscript figures, accepted for publication in Astronomy & Astrophysics, final version
dc.identifierhttps://arxiv.org/abs/astro-ph/0411698
dc.identifierhttp://arxiv.org/abs/astro-ph/0411698
dc.identifierAstron.Astrophys. 434 (2005) 275
dc.identifierdoi:10.1051/0004-6361:20047060
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/8636
dc.subjectAstrophysics
dc.titleThe age of the Galactic thin disk from Th/Eu nucleocosmochronology I. Determination of [Th/Eu] abundance ratios
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