2004/11/30 by E. F. del Peloso, L. da Silva, G. F. Porto de Mello · 5 citations
Physics and Astronomy · #Astro and Planetary Science #Astronomical and nuclear sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1051/0004-6361:20047060
published as Astron.Astrophys. 434 (2005) 275 · 27 pages, 22 Postscript figures, accepted for publication in Astronomy & Astrophysics, final version
arxiv created 2005/02/21 · openalex publication_date 2005/04/01 · arxiv updated 2009/12/01 · openalex created_date 2022/10/01 · openalex updated_date 2026/07/31
The 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 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. An homogeneous, self-consistent set of atmospheric parameters was determined. Effective temperatures were determined from photometric calibrations and Hα profile fitting; surface gravities were obtained from , stellar masses and luminosities; microturbulence velocities and metallicities were obtained from detailed, differential spectroscopic analysis, relative to the Sun, using equivalent widths of and 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 – () dex – being found to be satisfactorily low. Eu and Th abundances were determined by spectral synthesis of one line (4129.72 Å) and one line (4019.13 Å), 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.