Journal
ASTRONOMY & ASTROPHYSICS
Volume 607, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201731948
Keywords
nuclear reactions, nucleosynthesis, abundances; stars: interiors; stars: chemically peculiar; stars: abundances; stars: massive
Categories
Funding
- Swiss National Science Foundation [200020-172505]
- World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan
- ChETEC COST Action [CA16117]
- COST (European Cooperation in Science and Technology)
- European Research Council under the European Union's Seventh Framework Programme (FP)/ERC Grant [306901]
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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 25 M-boxed dot source star with v(ini) similar to 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.
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