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The Evolution of Binary Fractions in Globular Clusters

N. Ivanova·K. Belczynski·J. M. Fregeau·F. A. Rasio
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Abstract

We study the evolution of binary stars in globular clusters using a new Monte Carlo approach combining a population synthesis code (StarTrack), and a simple treatment of dynamical interactions in the dense cluster core using a new tool for computing 3-body and 4-body interactions (Fewbody). We find that the combination of stellar evolution and dynamical interactions (binary-single and binary-binary) leads to a rapid depletion of the binary population in the cluster core. The maximum binary fraction today in the core of a typical dense cluster like 47 Tuc, assuming an initial binary fraction of 100%, is only about 5-10%. We show that this is in good agreement with recent HST observations of close binaries in the core of 47 Tuc, provided that a realistic distribution of binary periods is used to interpret the results. Our findings also have important consequences for the dynamical modeling of globular clusters, suggesting that ``realistic models'' should incorporate much larger initial binary fractions than has usually been done in the past.

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N. Ivanova, K. Belczynski, J. M. Fregeau, F. A. Rasio. 2005-01-07. The Evolution of Binary Fractions in Globular Clusters. https://doi.org/10.1111/j.1365-2966.2005.08804.x

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