Relativistic Binaries in Globular Clusters

TL;DR

This review explores the formation, evolution, and observational evidence of relativistic binaries in globular clusters, emphasizing theoretical models, simulation techniques, and potential gravitational wave detections.

Contribution

It provides a comprehensive overview of models and simulations predicting relativistic binary populations in globular clusters, including recent observational findings and future prospects.

Findings

Globular clusters host diverse relativistic binary systems.

Simulations predict significant populations of relativistic binaries.

Observations include millisecond pulsars and X-ray binaries.

Abstract

Galactic globular clusters are old, dense star systems typically containing 10\super{4}--10\super{7} 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 theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of hard binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct {\it 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.