Star Cluster Evolution with Primordial Binaries

Observations and theoretical work suggest that globular clus- ters may be born with initially very large binary fractions. We present first results from our newly modified Monte-Carlo cluster evolution code, which treats binary interactions exactly via direct N -body integration. It is shown that binary scattering interactions generate significantly less energy than predicted by the recipes that have been used in the past to model them in approximate cluster evolution methods. The new result, that the cores of globular clusters in the long-lived binary-burning phase are smaller than previously predicted, weakens the agreement with obser- vations, thus implying that more than simply stellar dynamics is at work in shaping the globular clusters we observe today.