Abstract
The galactic population of globular clusters are old, dense star systems, with a typical cluster containing 104 – 106 stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss the theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution which lead to relativistic binaries, and current and possible future observational evidence for this population. Globular cluster evolution will focus on the properties that boost the production of hard binary systems and on the tidal interactions of the galaxy with the cluster, which tend to alter the structure of the globular cluster with time. The interaction of the components of hard binary systems alters the evolution of both bodies and can lead to exotic objects. Direct N-body integrations and Fokker-Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.
Highlights
Binaries containing white dwarfs, neutron stars, and black holes in compact orbits are overrepresented in globular clusters compared with their population in the galactic field
Considering that the time for a close passage of two neutron stars is on the order of milliseconds and that the age of a globular cluster is 1010 yr ∼ 1020 ms, we find that the time scales span 20 orders of magnitude
Noting that each encounter increases the binding energy by about 20% and that roughly 1/3 of this energy goes into binary recoil, the minimum binding energy Eb min of an ejected black hole binary is where M is the average mass of a globular cluster star and W0 = M |φ0|/kT is the dimensionless central potential
Summary
On author request a Living Reviews article can be amended to include errata and small additions to ensure that the most accurate and up-to-date information possible is provided. For detailed documentation of amendments, please go to the article’s online version at http://www.livingreviews.org/lrr-2002-2/. Owing to the fact that a Living Reviews article can evolve over time, we recommend to cite the article as follows: Matthew J. Benacquista, “Relativistic Binaries in Globular Clusters”, Living Rev. Relativity, 5, (2002), 2. [Online Article]: cited [], http://www.livingreviews.org/lrr-2002-2 The date in ’cited []’ uniquely identifies the version of the article you are referring to Relativity, 5, (2002), 2. [Online Article]: cited [], http://www.livingreviews.org/lrr-2002-2 The date in ’cited []’ uniquely identifies the version of the article you are referring to
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