Eccentricity Boost of Stars Around Shrinking Massive Black Hole Binaries

摘要

Based on a simple geometrical approach, we analyze the evolution of theKozai-Lidov mechanism for stars around shrinking massive black hole binaries oncircular orbits. We find that, due to a peculiar bifurcation pattern induced bythe Newtonian potential of stellar clusters, the orbit of stars could becomehighly eccentric. This transition occurs abruptly for stars with small initialeccentricities. Our approach would be also useful for studying the Kozai-Lidovmechanism in various astrophysical contexts.