SCYON Abstract

Received on April 15 2008

Chemical composition of A and F dwarfs members of the Pleiades open cluster

AuthorsM. Gebran (1) and R. Monier (2)
Affiliation(1) Groupe de Recherche en Astronomie et Astrophysique du Languedoc,UMR 5024, Université Montpellier II, Place Eugéne Bataillon, 34095 Montpellier, France
(2) Laboratoire Universitaire d'Astrophysique de Nice, UMR 6525, Université de Nice - Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France
Accepted byAstronomy & Astrophysics
Contactgebran@graal.univ-montp2.fr
URLhttp://arxiv.org/abs/0802.3148
Links Pleiades

Abstract

We derive the abundances of 18 chemical elements for 16 A-dwarf, both normal and chemically-peculiar, and 5 F-dwarf members of the Pleiades open cluster to place constraints on evolutionary models. Abundances and rotational and microturbulent velocities were derived by fitting synthetic spectra to high-resolution (R ~ 42000 and R ~ 75000) observations of high signal-to-noise ratio (S/N). The abundances exhibit correlation with neither the effective temperature nor the projected rotational velocity. Interestingly, A stars exhibit larger star-to-star variations in C, Sc, Ti, V, Cr, Mn, Sr, Y, Zr and Ba, than F stars. F stars have solar abundances of almost all elements. In A stars, the abundances of Si, Ti and Cr are correlated with that of Fe, and the [X/Fe] ratios are solar for these three elements. The derived abundances are compared with the predictions of evolutionary models for the age of Pleiades (100 Myr). For F stars, small predicted underabundances of light elements and overabundances of Cr, Fe and Ni are confirmed by our findings. For A stars, the predicted overabundances in iron-peak elements are confirmed for a few stars only. The large scatter in the abundances of A stars, discovered previously in the Hyades, Coma Berenices, UMa group, and in field stars, appears to be a characteristic property of dwarf A stars. Hydrodynamical processes competing with radiative diffusion in the radiative zone of A dwarfs, could account for the scatter in abundances that we determine.