New analysis of the two carbon-rich stars CS 22948-27 and CS 29497-34: Binarity and neutron capture elements^*

¹ Universidade de São Paulo, Rua do Matão 1226, São Paulo 05508-900, Brazil e-mail: barbuy@astro.iag.usp.br
² Observatoire de Paris-Meudon, GEPI, URM 8633 du CNRS, 92195 Meudon Cedex, France
³ Observatoire de Paris, GEPI, 61 Av. de l'Observatoire, 75014 Paris, France
⁴ GRAAL cc72, Université de Montpellier II, 34095 Montpellier Cedex 5, France
⁵ Institut d'Astrophysique, 98bis Bd. Arago, 75014 Paris, France

Received: 9 March 2004
Accepted: 27 August 2004

Abstract

We have carried out a new determination of abundances in the very metal-poor CH/CN strong stars CS 22948-27 and CS 29497-34, using high-resolution spectra obtained with the HARPS spectrograph at the 3.6 m telescope of ESO, La Silla, that covers the range  4000-6900 Å at a resolution of . Both stars are found to be long period binaries. It is confirmed that the abundance patterns show an enhancement of the α-elements (like Mg, Ca), of the proton capture elements (like Na and Al) and a strong enrichment in “r” and “s” process elements, where the s-enrichment is probably due to a mass transfer episode from a companion in its AGB phase. The possible origins of the abundance pattern and especially of the strong enhancement of both “s” and “r” elements are discussed.