Evolution of the Binary Fraction in Dense Stellar Systems

Using our recently improved Monte Carlo evolution code, we study the evolution of the binary fraction in globular clusters. In agreement with previous N-body simulations, we find generally that the hard binary fraction in the core tends to increase with time over a range of initial cluster central d...

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Bibliographic Details
Published in:The Astrophysical journal 2009-12, Vol.707 (2), p.1533-1540
Main Authors: Fregeau, John M, Ivanova, Natalia, Rasio, Frederic A
Format: Article
Language:English
Subjects:
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CALCULATION METHODS
DENSITY
EVOLUTION
INDICATORS
MAIN SEQUENCE STARS
MASS
MONTE CARLO METHOD
NONLINEAR PROBLEMS
PHYSICAL PROPERTIES
SEGREGATION
SIMULATION
STAR EVOLUTION
STARS
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Summary:Using our recently improved Monte Carlo evolution code, we study the evolution of the binary fraction in globular clusters. In agreement with previous N-body simulations, we find generally that the hard binary fraction in the core tends to increase with time over a range of initial cluster central densities for initial binary fractions 90%. The dominant processes driving the evolution of the core binary fraction are mass segregation of binaries into the cluster core and preferential destruction of binaries there. On a global scale, these effects and the preferential tidal stripping of single stars tend to roughly balance, leading to overall cluster binary fractions that are roughly constant with time. Our findings suggest that the current hard binary fraction near the half-mass radius is a good indicator of the hard primordial binary fraction. However, the relationship between the true binary fraction and the fraction of main-sequence stars in binaries (which is typically what observers measure) is nonlinear and rather complicated. We also consider the importance of soft binaries, which not only modify the evolution of the binary fraction, but can also drastically change the evolution of the cluster as a whole. Finally, we briefly describe the recent addition of single and binary stellar evolution to our cluster evolution code.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/707/2/1533