Are some CEMP-s stars the daughters of spinstars?

Choplin, Arthur; Hirschi, Raphael; Meynet, Georges; Ekström, Sylvia

Abstract

Carbon-enhanced metal-poor (CEMP)-s stars are long-lived low-mass stars with a very low iron content as well as overabundances of carbon and s-elements. Their peculiar chemical pattern is often explained by pollution from an asymptotic giant branch (AGB) star companion. Recent observations have shown that most CEMP-s stars are in binary systems, providing support to the AGB companion scenario. A few CEMP-s stars, however, appear to be single. We inspect four apparently single CEMP-s stars and discuss the possibility that they formed from the ejecta of a previous-generation massive star, referred to as the “source” star. In order to investigate this scenario, we computed low-metallicity massive-star models with and without rotation and including complete s-process nucleosynthesis. We find that non-rotating source stars cannot explain the observed abundance of any of the four CEMP-s stars. Three out of the four CEMP-s stars can be explained by a 25M? source star with vini ~ 500 km?s-1 (spinstar). The fourth CEMP-s star has a high Pb abundance that cannot be explained by any of the models we computed. Since spinstars and AGB predict different ranges of [O/Fe] and [ls/hs], these ratios could be an interesting way to further test these two scenarios. nuclear reactions, nucleosynthesis, abundances / stars: interiors / stars: chemically peculiar / stars: abundances / stars: massive

Citation

Choplin, A., Hirschi, R., Meynet, G., & Ekström, S. (2017). Are some CEMP-s stars the daughters of spinstars?. Astronomy and Astrophysics, 607, Article L3. https://doi.org/10.1051/0004-6361/201731948

• Journal Article Type: Article
• Acceptance Date: Oct 16, 2017
• Online Publication Date: Oct 16, 2017
• Publication Date: 2017-11
• Publicly Available Date: May 26, 2023
• Journal: Astronomy and Astrophysics
• Print ISSN: 2329-1273
• Publisher: Hans Publishers
• Peer Reviewed: Peer Reviewed
• Volume: 607
• Article Number: L3
• DOI: https://doi.org/10.1051/0004-6361/201731948
• Keywords: nuclear reactions, nucleosynthesis, abundances, stars, interiors, chemically peculiar, massive
• Publisher URL: http://doi.org/10.1051/0004-6361/201731948