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Evolution of binary stars and its implications for evolutionary population synthesis

Published online by Cambridge University Press:  13 April 2010

Z. Han ,
X. Chen ,
F. Zhang  and
Ph. Podsiadlowski
Z. Han
Affiliation:
National Astronomical Observatories/Yunnan Observatory, the Chinese Academy of Sciences, Kunming, 650011, China (email: zhanwenhan@ynao.ac.cn)
X. Chen
Affiliation:
National Astronomical Observatories/Yunnan Observatory, the Chinese Academy of Sciences, Kunming, 650011, China (email: zhanwenhan@ynao.ac.cn)
F. Zhang
Affiliation:
National Astronomical Observatories/Yunnan Observatory, the Chinese Academy of Sciences, Kunming, 650011, China (email: zhanwenhan@ynao.ac.cn)
Ph. Podsiadlowski
Affiliation:
University of Oxford, Department of Astrophysics, Keble Road, Oxford, OX1 3RH, UK
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Abstract

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Most stars are members of binaries, and the evolution of a star in a close binary system differs from that of an ioslated star due to the proximity of its companion star. The components in a binary system interact in many ways and binary evolution leads to the formation of many peculiar stars, including blue stragglers and hot subdwarfs. We will discuss binary evolution and the formation of blue stragglers and hot subdwarfs, and show that those hot objects are important in the study of evolutionary population synthesis (EPS), and conclude that binary interactions should be included in the study of EPS. Indeed, binary interactions make a stellar population younger (hotter), and the far-ultraviolet (UV) excess in elliptical galaxies is shown to be most likely resulted from binary interactions. This has major implications for understanding the evolution of the far-UV excess and elliptical galaxies in general. In particular, it implies that the far-UV excess is not a sign of age, as had been postulated prviously and predicts that it should not be strongly dependent on the metallicity of the population, but exists universally from dwarf ellipticals to giant ellipticals.

Keywords

stars: binaries: close – stars: blue stragglers – stars: subdwarfs – galaxies: elliptical and lenticularcD – ultraviolet: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S262: Stellar Populations – Planning for the Next Decade , August 2009 , pp. 44 - 47
Copyright
Copyright © International Astronomical Union 2010

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