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|Title:||The CEMP star SDSS J0222-0313: the first evidence of proton ingestion in very low-metallicity AGB stars?||Authors:||Caffau, E.
|Issue Date:||2019||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||628||First Page:||A46||Abstract:||Context. Carbon-enhanced metal-poor (CEMP) stars are common objects in the metal-poor regime. The lower the metallicity we look at, the larger the fraction of CEMP stars with respect to metal-poor stars with no enhancement in carbon. The chemical pattern of CEMP stars is diversified, strongly suggesting a different origin of the C enhancement in the different types of CEMP stars. <BR /> Aims: We selected a CEMP star, SDSS J0222-0313, with a known high carbon abundance and, from a low-resolution analysis, a strong enhancement in neutron-capture elements of the first peak (Sr and Y) and of the second peak (Ba). The peculiarity of this object is a greater overabundance (with respect to iron) of the first s-process peak than the second s-process peak. <BR /> Methods: We analysed a high-resolution spectrum obtained with the Mike spectrograph at the Clay Magellan 6.5 m telescope in order to derive the detailed chemical composition of this star. <BR /> Results: We confirmed the chemical pattern we expected; we derived abundances for a total of 18 elements and significant upper limits. <BR /> Conclusions: We conclude that this star is a carbon-enhanced metal-poor star enriched in elements produced by s-process (CEMP-s), whose enhancement in heavy elements is due to mass transfer from the more evolved companion in its asymptotic giant branch (AGB) phase. The abundances imply that the evolved companion had a low main sequence mass and it suggests that it experienced a proton ingestion episode at the beginning of its AGB phase. <P />Based on observations collected with Mike at the Magellan-II (Clay) telescope at the Las Campanas Observatory under programme CN2018B-5.||URI:||http://hdl.handle.net/20.500.12386/28661||URL:||https://www.aanda.org/articles/aa/full_html/2019/08/aa35680-19/aa35680-19.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201935680||Bibcode ADS:||2019A&A...628A..46C||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Jan 22, 2021
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