1997/10/21 by M. Kunzli, M. Künzli, Kunzli, M. +2
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #Astrophysics and Star Formation Studies #FOS: Physical sciences #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9710223
9 pages, 8 figures, accepted for A&A
arxiv created 1997/10/21 · openalex publication_date 1997/10/21 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Calcium abundance in the atmosphere of Am stars is examined as a function of their evolutionary state within the main sequence. New spectroscopic abundances as well as abundances abtained photometrically by Guthrie (1987) are used, since they are mutually quite consistent. The main result of this work is that, contrary to earlier suggestions, calcium abundance does not tend to be larger in evolved Am stars than in unevolved ones, for objects distributed along a given evolutionary track in the HR diagram. The trend appears to be the reverse, if it is present at all. For our whole sample of Am stars, there is a significant correlation between calcium abundance and effective temperature, in the sense that the cooler objects are the most Ca-deficient, hance have the most pronounced Am peculiarity. This implies an apparent correlation between calcium deficiency and age, although the lack of Am stars younger than log(t) = 8.6 seems real. Our results are fully consistent with the low rate of Am stars observed in young clusters and with theoretical predictions of time-dependent radiative diffusion (Alecian 1996).