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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Wind Roche-lobe overflow: Application to carbon-enhanced metal-poor stars
Astronomy and Astrophysics, Volume 552, Article A26, Year 2013
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Description
Carbon-enhanced metal-poor (CEMP) stars are observed as a substantial fraction of the very metal-poor stars in the Galactic halo. Most CEMP stars are also enriched in s-process elements, and these are often found in binary systems. This suggests that the carbon enrichment is due to mass transfer in the past from an asymptotic giant branch (AGB) star on to a low-mass companion. Models of binary population synthesis are not able to reproduce the observed fraction of CEMP stars without invoking non-standard nucleosynthesis or a substantial change in the initial mass function. This is interpreted as evidence of missing physical ingredients in the models. Recent hydrodynamical simulations show that efficient wind mass transfer is possible in the case of the slow and dense winds typical of AGB stars through a mechanism called wind Roche-lobe overflow (WRLOF), which lies in between the canonical Bondi-Hoyle-Lyttleton (BHL) accretion and Roche-lobe overflow. WRLOF has an effect on the accretion efficiency of mass transfer and on the angular momentum lost by the binary system. The aim of this work is to understand the overall effect of WRLOF on the population of CEMP stars. To simulate populations of low-metallicity binaries we combined a synthetic nucleosynthesis model with a binary population synthesis code. In this code we implemented the WRLOF mechanism. We used the results of hydrodynamical simulations to model the effect of WRLOF on the accretion efficiency, and we took the effect on the angular momentum loss into account by assuming a simple prescription. The combination of these two effects widens the range of systems that become CEMP stars towards longer initial orbital periods and lower mass secondary stars. As a consequence the number of CEMP stars predicted by our model increases by a factor 1.2-1.8 compared to earlier results that consider the BHL prescription. Moreover, higher enrichments of carbon are produced, and the final orbital period distribution is shifted towards shorter periods. © ESO, 2013.
Authors & Co-Authors
Abate, C.
Netherlands, Nijmegen
Radboud Universiteit
Pols, O. R.
Netherlands, Nijmegen
Radboud Universiteit
Izzard, Robert G.
Germany, Bonn
Universität Bonn
Mohamed, S. S.
Germany, Bonn
Universität Bonn
South Africa, Cape Town
South African Astronomical Observatory
de Mink, Selma E.
United States, Baltimore
Space Telescope Science Institute
United States, Baltimore
Johns Hopkins University
Statistics
Citations: 114
Authors: 5
Affiliations: 5
Identifiers
Doi:
10.1051/0004-6361/201220007
ISSN:
00046361
e-ISSN:
14320746
Research Areas
Environmental
Study Design
Cross Sectional Study