Metal abundances of field A and Am stars^*

Laboratoire d'Astrophysique Extragalactique et de Cosmologie, CNRS (UMR 8631), Observatoire de Paris, Université Paris 7, DAEC, Observatoire de Meudon, F–92195 Meudon Cedex, France

Send offprint request to: A. Hui-Bon-Hoa

Received: 12 April 1999
Accepted: 25 February 2000

Abstract


Detailed abundances of 9 field A and Am stars are derived for Mg, Ca, Sc, Cr, Fe, and Ni using high resolution spectroscopy. Most of our sample Am stars show the characteristic deficiencies of Ca and Sc on one hand, and the overabundances of the iron peak elements on the other, which is consistent with the predictions of the diffusion model for Main Sequence or slightly evolved stars. There seems to be a correlation between abundances of Ca and Sc and the effective temperature for stars of similar age: the abundance of Ca increases with increasing mass whereas that of Sc decreases. Two of our Am stars have a different abundance pattern: Ca is overabundant in the hot magnetic Am star o Peg and its abundance is nearly normal in the metallic giant star ρ  Pup. The other objects of our sample have globally a solar composition except 28 And, which shows significant deficiencies for most the studied elements.