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The binary frequency among carbon-enhanced, s-process-rich, metal-poor stars

Lucatello, S.; Tsangarides, S.; Beers, T. C.; Carretta, E.; Gratton, R. G. and Ryan, S. G. (2005). The binary frequency among carbon-enhanced, s-process-rich, metal-poor stars. Astrophysical Journal, 625(2) pp. 825–832.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1086/428104
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Abstract

We discuss radial velocities for a sample of carbon-enhanced, s-process-rich, very metal-poor (CEMP-s) stars, analyzed with high-resolution spectroscopy obtained over multiple epochs. We find that similar to 68% of the stars in the sample show evidence of radial velocity variations. The expected detection fraction for these stars, adopting the measured binary fraction in the field (similar to 60%) and assuming that they share the same period and eccentricity distribution, is similar to 22%. Even if one assumes that the true binary fraction of these stars is 100%, the expected detection percentage is similar to 36%. These values indicate that the binary fraction among CEMP-s stars is higher than the field binary fraction, suggesting that all of these objects are in double ( or multiple) systems. The fact that the observed frequency of velocity variation exceeds the expected detection fraction in the case of an assumed binary fraction of 100% is likely due to a more restricted distribution of orbital periods for these objects, as compared to normal field binaries. Our results indicate that CEMP-s stars are the metal-poor analogs of classical CH stars.

Item Type: Journal Article
Copyright Holders: 2005 The American Astronomical Society
ISSN: 1538-4357
Academic Unit/Department: Science > Physical Sciences
Item ID: 18228
Depositing User: Colin Smith
Date Deposited: 04 Sep 2009 09:39
Last Modified: 28 Jan 2014 10:43
URI: http://oro.open.ac.uk/id/eprint/18228
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