The field Am and ρ Puppis-like stars: Lithium and heavier elements ^*

¹ Observatoire de Lyon (Un. Lyon I) and UMR 5574 (CNRS), 69561 Saint-Genis-Laval Cedex, France e-mail: burkhart@obs.univ-lyon1.fr
² Observatoire de Paris and URA 335 (CNRS), 61 Av. de l'Observatoire, 75014 Paris, France
³ Dipartimento di Astronomia, Università degli Studi di Trieste, via G.B. Tiepolo 11, 34131, Trieste, Italy
⁴ Institut d'Astrophysique, 98bis Bd Arago, 75014 Paris, France
⁵ Lab. Astronomie, Bât. 470, Université de Paris-Sud XI, 91405 Orsay Cedex, France

Received: 18 March 2004
Accepted: 27 August 2004

Abstract

With observations at the Canada-France-Hawaii telescope, photospheric abundances of two evolved field Am stars, τ UMa and HR 178, have been determined for Li, Al, Si, S, Fe, Ni, and Eu by model abundance analysis. Thanks to these new determined abundances and the HIPPARCOS mission, making it possible to better estimate the evolutionary stage of field stars, one can consider the influence of evolution on the abundances of Am stars. No abundance trend for Al, Si, S, and Fe is found during Main Sequence evolution, up to its very last phases. The abundance of Li is, generally, cosmic. Large Li deficiencies may be observed in the very last phases (the “hook” region of the H-R diagram) and, too, on the red side of the Am phenomenon region where the ρ Puppis-like stars lie.