English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The detailed composition of most metal-poor halo stars has been found to bevery uniform. However, a fraction of 20-70% (increasing with decreasingmetallicity) exhibit dramatic enhancements in their abundances of carbon - theso-called carbon-enhanced metal-poor (CEMP) stars. A key question for Galacticchemical evolution models is whether this non-standard composition reflectsthat of the stellar natal clouds, or is due to local, post-birth mass transferof chemically processed material from a binary companion; CEMP stars shouldthen all be members of binary systems. Our aim is to determine the frequencyand orbital parameters of binaries among CEMP stars with and withoutover-abundances of neutron-capture elements - CEMP-s and CEMP-no stars,respectively - as a test of this local mass-transfer scenario. This paperdiscusses a sample of 24 CEMP-no stars, while a subsequent paper will considera similar sample of CEMP-s stars. Most programme stars exhibit no statisticallysignificant radial-velocit variation over this period and appear to be single,while four are found to be binaries with orbital periods of 300-2,000 days andnormal eccentricity; the binary frequency for the sample is 17+-9%. The singlestars mostly belong to the recently-identified ``low-C band'', while thebinaries have higher absolute carbon abundances. We conclude that thenucleosynthetic process responsible for the strong carbon excess in theseancient stars is unrelated to their binary status; the carbon was imprinted ontheir natal molecular clouds in the early Galactic ISM by an even earlier,external source, strongly indicating that the CEMP-no stars are likely bonafide second-generation stars. We discuss potential production sites for carbonand its transfer across interstellar distances in the early ISM, andimplications for the composition of high-redshift DLA systems. Abridged.

The role of binaries in the enrichment of the early Galactic halo. II. Carbon-Enhanced Metal-Poor Stars - CEMP-no stars