uu.seUppsala University Publications
Change search
ReferencesLink to record
Permanent link

Direct link
The most metal-poor stars. IV. the two populations with [Fe/H] ≲ -3.0
Show others and affiliations
2013 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 762, no 1, 28- p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2013. Vol. 762, no 1, 28- p.
Keyword [en]
early universe, Galaxy: formation, Galaxy: halo, nuclear reactions, nucleosynthesis, abundances, stars: abundances
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-192033DOI: 10.1088/0004-637X/762/1/28ISI: 000313007900028OAI: oai:DiVA.org:uu-192033DiVA: diva2:589985
Available from: 2013-01-21 Created: 2013-01-15 Last updated: 2013-02-05Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Search in DiVA

By author/editor
Barklem, Paul. S.
By organisation
Theoretical Astrophysics
In the same journal
Astrophysical Journal
Natural Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 527 hits
ReferencesLink to record
Permanent link

Direct link