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|Title:||Observational Constraints on First-star Nucleosynthesis. I. Evidence for Multiple Progenitors of CEMP-No Stars||Authors:||Yoon, Jinmi
Beers, Timothy C.
Placco, Vinicius M.
Rasmussen, Kaitlin C.
Hansen, Terese T.
Roederer, Ian U.
|Issue Date:||2016||Journal:||THE ASTROPHYSICAL JOURNAL||Number:||833||Issue:||1||First Page:||20||Abstract:||We investigate anew the distribution of absolute carbon abundance, A(C) = log ∊(C), for carbon-enhanced metal-poor (CEMP) stars in the halo of the Milky Way, based on high-resolution spectroscopic data for a total sample of 305 CEMP stars. The sample includes 147 CEMP-s (and CEMP-r/s) stars, 127 CEMP-no stars, and 31 CEMP stars that are unclassified, based on the currently employed [Ba/Fe] criterion. We confirm previous claims that the distribution of A(C) for CEMP stars is (at least) bimodal, with newly determined peaks centered on A(C) = 7.96 (the high-C region) and A(C) = 6.28 (the low-C region). A very high fraction of CEMP-s (and CEMP-r/s) stars belongs to the high-C region, while the great majority of CEMP-no stars resides in the low-C region. However, there exists complexity in the morphology of the A(C)-[Fe/H] space for the CEMP-no stars, a first indication that more than one class of first-generation stellar progenitors may be required to account for their observed abundances. The two groups of CEMP-no stars we identify exhibit clearly different locations in the A(Na)-A(C) and A(Mg)-A(C) spaces, also suggesting multiple progenitors. The clear distinction in A(C) between the CEMP-s (and CEMP-r/s) stars and the CEMP-no stars appears to be as successful, and likely more astrophysically fundamental, for the separation of these sub-classes as the previously recommended criterion based on [Ba/Fe] (and [Ba/Eu]) abundance ratios. This result opens the window for its application to present and future large-scale low- and medium-resolution spectroscopic surveys.||URI:||http://hdl.handle.net/20.500.12386/30940||URL:||https://iopscience.iop.org/article/10.3847/0004-637X/833/1/20||ISSN:||0004-637X||DOI:||10.3847/0004-637X/833/1/20||Bibcode ADS:||2016ApJ...833...20Y||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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checked on Jun 15, 2021
checked on Jun 15, 2021
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