1999/06/03 by P. Bonifacio, M. Centurión, M. Centurion +1 · 2 citations
Chemistry · Physics and Astronomy · #Abundance (ecology) #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Chemistry #Galactic halo #Galaxy #Halo #Metal #Metallicity #Physics #Proper motion #Spectral line #Stars #Stellar, planetary, and galactic studies #Thick disk #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1999.02866.x
to be published in MNRAS
arxiv created 1999/06/03 · openalex publication_date 1999/10/21 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
High-resolution spectra of five candidate metal-weak thick-disc stars suggested by Beers & Sommer-Larsen are analysed to determine their chemical abundances. The low abundance of all the objects has been confirmed, with metallicity reaching [Fe/H] = −2.9. However, for three objects the astrometric data from the Hipparcos catalogue suggest they are true halo members. The remaining two, for which proper-motion data are not available, may have disc-like kinematics. It is therefore clear that it is useful to address properties of putative metal-weak thick-disc stars only if they possess full kinematic data. For CS 22894-19 an abundance pattern similar to those of typical halo stars is found, suggesting that chemical composition is not a useful discriminant between thick-disc and halo stars. CS 29529-12 is found to be C-enhanced with [C/Fe] = +1.0; other chemical peculiarities involve the s-process elements: [Sr/Fe] = −0.65 and [Ba/Fe] = +0.62, leading to a high [Ba/Sr], considerably larger than that found in more metal-rich carbon-rich stars, but similar to those in LP 706-7 and LP 625-44, discussed by Norris et al. Hipparcos data have been used to calculate the space velocities of 25 candidate metal-weak thick-disc stars, thus allowing us to identify three bona fide members, which support the existence of a metal-poor tail of the thick disc, at variance with a claim to the contrary by Ryan & Lambert.