2000/01/21 by M. Salaris, Salaris, M., M. A. T. Groenewegen +4
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #Diffusion #FOS: Physical sciences #Galaxy #Globular cluster #Halo #Horizontal branch #Metallicity #Physics #Population #Stars #Stellar, planetary, and galactic studies #Thermodynamics #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0001386
published in arXiv (Cornell University) (Cornell University) · 10 pages, 7 figures, accepted for publication in A&A (main journal)
arxiv created 2000/01/21 · openalex publication_date 2000/01/21 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
The effect of atomic diffusion on the Main Sequence (MS) of metal-poor low mass stars is investigated. Since diffusion alters the stellar surface chemical abundances with respect to their initial values, one must ensure - by calibrating the initial chemical composition of the theoretical models - that the surface abundances of the models match the observed ones of the stellar population under scrutiny. Since the observed surface abundances of subdwarfs are different from the initial ones due to the effect of diffusion, while the globular clusters stellar abundances are measured in Red Giants, which have practically recovered their initial abundances after the dredge-up, the isochrones to be employed for studying globular clusters and Halo subdwarfs with the same observational value of [Fe/H] are different and do not coincide. We find, however,that the current MS-fitting distances derived from HIPPARCOS subdwarfs using colour corrections from standard isochrones are basically unaltered when diffusion is taken properly into account; on the other hand, the absolute ages, the age dispersion, the age-metallicity relation for Halo subdwarfs, as well as the value of the helium enrichment ratio Delta Y/Delta Z obtained from the width of the empirical Halo subdwarfs MS, are all significantly modified when the properly calibrated isochrones with diffusion are used.