SCYON Abstract

Received on October 3 2006

Collisional Hardening of Compact Binaries in Globular Clusters

Authors	S. Banerjee and P. Ghosh
Affiliation	Tata Institute of Fundamental Research, Mumbai
Accepted by	Monthly Notices of the Royal Astronomical Society
Contact	pranab@mailhost.tifr.res.in sambaran@mailhost.tifr.res.in
URL	http://xxx.lanl.gov/abs/astro-ph/0609816
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Abstract

We consider essential mechanisms for orbit-shrinkage or "hardening" of compact binaries in globular clusters to the point of Roche-lobe contact and X-ray emission phase, focussing on the process of collisional hardening due to encounters between binaries and single stars in the cluster core. The interplay between this kind of hardening and that due to emission of gravitational radiation produces a characteristic scaling of the orbit-shrinkage time with the single-star binary encounter rate γ in the cluster which we introduce, clarify, and explore. We investigate possible effects of this scaling on populations of X-ray binaries in globular clusters within the framework of a simple "toy" scheme for describing the evolution of pre-X-ray binaries in globular clusters. We find the expected qualitative trends sufficiently supported by data on X-ray binaries in galactic globular clusters to encourage us toward a more quantitative study.