Dynamical effects on binary X-ray sources in dense stellar clusters

We examine the model in which the globular-cluster X-ray sources are binaries. Collisions of field stars in cores of dense clusters may shrink the orbits of tightly bound (''hard'') binaries, with important consequences for the evolution of X-ray sources if one component is a collapsed star. Exchange capture of field stars enables the binary to recycle its mass supplier and to undergo a number of intermittent stages of X-ray activity. ''Hard'' binaries may be formed by three-body encounters or by two-body tidal capture in clusters with large core densities and low velocity dispersions. Alternatively, as suggested by Hills, such objects may form by neutron-star or black-hole capture in exchange collisions with primordial binaries