Abundance determinations in A and F dwarfs in open clusters

Abstract

The current status of abundance determinations for A and F dwarfs in open clusters is reviewed. An observational programme was launched a few years ago to observe a large number of A/F and Am/Fm dwarfs in open clusters of various ages. The status of that particular programme is also reviewed. High resolution high S/N spectroscopy of a large number of stars well distributed in mass along the Main Sequence was secured. Abundances of 11 chemical elements have been derived by iteratively fitting synthetic spectra calculated in LTE to the observed spectra. The results obtained are reviewed for the Hyades and Coma Berenices. New abundance determinations for 24 A and F dwarfs in the Ursa Major moving group are presented. In all three clusters, a pronounced scatter of the abundances versus effective temperature for most chemical elements is found for the A dwarfs. In contrast, the abundances of F dwarfs are much less scattered around their mean value. These abundance determinations are useful to set constraints to self-consistent evolutionnary models of A and F dwarfs including transport processes. Directions for future work in particular to derive more accurate abundances are outlined.