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The most metal-poor...
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Norris, J. E.
(författare)
The most metal-poor stars. IV. the two populations with [Fe/H] ≲ -3.0
- Artikel/kapitelEngelska2013
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LIBRIS-ID:oai:DiVA.org:uu-192033
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https://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-192033URI
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https://doi.org/10.1088/0004-637X/762/1/28DOI
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Språk:engelska
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Sammanfattning på:engelska
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Ämneskategori:ref swepub-contenttype
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Ämneskategori:art swepub-publicationtype
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We discuss the carbon-normal and carbon-rich populations of Galactic halo stars having [Fe/H] ≲ -3.0, utilizing chemical abundances from high-resolution, high signal-to-noise model-atmosphere analyses. The C-rich population represents ∼28% of stars below [Fe/H] = -3.1, with the present C-rich sample comprising 16 CEMP-no stars, and two others with [Fe/H] ∼ -5.5 and uncertain classification. The population is O-rich ([O/Fe] ≳ +1.5); the light elements Na, Mg, and Al are enhanced relative to Fe in half the sample; and for Z > 20 (Ca) there is little evidence for enhancements relative to solar values. These results are best explained in terms of the admixing and processing of material from H-burning and He-burning regions as achieved by nucleosynthesis in zero-heavy-element models in the literature of "mixing and fallback" supernovae (SNe); of rotating, massive, and intermediate-mass stars; and of Type II SNe with relativistic jets. The available (limited) radial velocities offer little support for the C-rich stars with [Fe/H] < -3.1 being binary. More data are required before one could conclude that binarity is key to an understanding of this population. We suggest that the C-rich and C-normal populations result from two different gas cooling channels in the very early universe of material that formed the progenitors of the two populations. The first was cooling by fine-structure line transitions of C II and O I (to form the C-rich population); the second, while not well defined (perhaps dust-induced cooling?), led to the C-normal group. In this scenario, the C-rich population contains the oldest stars currently observed.
Ämnesord och genrebeteckningar
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early universe
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Galaxy: formation
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Galaxy: halo
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nuclear reactions
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nucleosynthesis
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abundances
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stars: abundances
Biuppslag (personer, institutioner, konferenser, titlar ...)
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Yong, D.
(författare)
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Bessell, M. S.
(författare)
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Christlieb, N.
(författare)
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Asplund, M.
(författare)
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Gilmore, G.
(författare)
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Wyse, R. F. G.
(författare)
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Beers, T. C.
(författare)
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Barklem, Paul. S.Uppsala universitet,Teoretisk astrofysik(Swepub:uu)pba11670
(författare)
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Frebel, A.
(författare)
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Ryan, S. G.
(författare)
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Uppsala universitetTeoretisk astrofysik
(creator_code:org_t)
Sammanhörande titlar
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Ingår i:Astrophysical Journal762:1, s. 28-0004-637X1538-4357
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Till lärosätets databas
- Av författaren/redakt...
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Norris, J. E.
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Yong, D.
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Bessell, M. S.
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Christlieb, N.
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Asplund, M.
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Gilmore, G.
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visa fler...
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Wyse, R. F. G.
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Beers, T. C.
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Barklem, Paul. S ...
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Frebel, A.
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Ryan, S. G.
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visa färre...
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Astrophysical Jo ...
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Uppsala universitet