Dynamical Effects Dominate the Evolution of Cataclysmic Variables in Dense Star Clusters

Strong interactions between the single and binary stars in the cores of dense clusters often cause the binaries' semimajor axes to contract. These "hardened" binaries are potent dynamical energy sources. Once significant physical interaction between a binary's components begins (e.g., mass transfer), the stellar evolution of that binary is intimately linked to the dynamical evolution of all the stars in the cluster. We self-consistently simulate the stellar dynamics, and binary and single-star evolution of a 100,000 star cluster with 5000 primordial binaries. The production of very close binaries containing a white dwarf is enhanced over that in the field; we focus on their formation, evolution, and fate. We report on a class of utterly novel CVs that never undergo a common envelope phase but are instead formed in exchange reactions. Exchange interactions are more likely to make CVs in which the main-sequence star mass is greater than 0.7 M☉, as opposed to CVs with low-mass donors. These dynamically produced CVs are more likely to be short-lived than their field counterparts. We find that the shorter lives of CVs in the harsh cluster environment decrease the expected number of CVs, at any given time, by a factor of 3. Finally, we provide the first self-consistent simulation of the period distribution of dynamics-dominated cataclysmic variables. We predict that there will be no 2-3 hour period gap for cluster CVs; the gap is smeared out by dynamical interactions of CVs with cluster stars.