Binary Formation and Interactions with Field Stars

Abstract

Binaries provide an energy source in dense stellar systems. Exothermic gravitational interactions in star clusters can play a role similar to that of nuclear reactions in single stars. These gravitational interactions can be modeled in a laboratory setting, in the form of numerical binary-single star and binary-binary scattering experiments. Gravitational cross sections obtained this way can be applied to model star cluster evolution, just as nuclear cross sections are used as input data in stellar evolution calculations. References are given to detailed descriptions of gravitational cross sections, and a useful new example of an application is given: the rate at which hard binaries form in a homogeneous stellar background, as the solution of an integral equation describing the combined effects of creation, destruction, hardening and softening of binaries.