Full text Author(s): Barbuy, B. [1] ; Spite, M. ; Spite, F. ; Hill, V. ; Cayrel, R. ; Plez, B. ; Petijean, P. Total Authors: 7 Affiliation: [1] Universidade de São Paulo (USP). Instituto de Astronomia, Geofísica e Ciências Atmosféricas - Brasil Total Affiliations: 7 Document type: Journal article Source: Astronomy & Astrophysics; v. 429, n. 3, p. 1031-1042, 2005. Field of knowledge: Physical Sciences and Mathematics - Astronomy 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 $\lambda\lambda$ 4000-6900 Å at a resolution of R = 100.000. Both stars are found to be long period binaries. It is confirmed that the abundance patterns show an enhancement of the $\alpha$-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. (AU) FAPESP's process: 00/10406-4 - Chemical evolution and stellar populations of the galaxy, magellanic clouds and elliptical galaxies, based on spectroscopy and imaging Grantee: Beatriz Leonor Silveira Barbuy Support type: Research Projects - Thematic Grants