Physics
Scientific paper
Mar 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aipc..990..161h&link_type=abstract
FIRST STARS III: First Stars II Conference. AIP Conference Proceedings, Volume 990, pp. 161-163 (2008).
Physics
2
Giant And Subgiant Stars, Chemical Composition And Chemical Evolution, Abundances, Chemical Composition, Origin, Formation, And Abundances Of The Elements, Stellar Structure, Interiors, Evolution, Nucleosynthesis, Ages
Scientific paper
Barium stars (the classical Ba, and dwarf Ba) are formed in binary systems. When the primary star is on the Asymptotic Giant Branch, mass transfer by efficient stellar winds takes place, from the carbon and s-element rich primary onto the secondary star, which is observed on the main sequence or on the subgiant/redgiant phase. The envelope of the secondary star becomes thus enriched in barium and s-elements. Dilution of the s-elements within the envelope may occur due to mixing processes. We have made a comparison between theoretical predictions of AGB stellar models and high-resolution spectroscopic observations of a large sample of barium stars [1,2]. Good agreement between predicted and observed enhancements of s-elements was found for most stars, including Pb. Values of [Pb/Fe]>1 dex have indeed been observed for the first time in Barium stars by Allen & Barbuy [1], and can easily be explained by adopting a high efficiency of the main 13C neutron source in AGB models, making a direct link with the class of very-metal poor C-rich and s-process rich stars (CEMP-s). The physical mechanism, mass transfer of C-rich and s-process rich material from the primary companion while on the AGB in a binary system is the same. The much higher [Pb/Fe] values that can be achieved in CEMP-s stars is explained by the primary nature of the 13C neutron source and by the decreasing of Fe seeds with metallicity.
Gallino Roberto
Husti Laura
Straniero Oscar
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