Busting Up Binaries: Encounters Between Compact Binaries and a Supermassive Black Hole

Close encounters between compact object binaries and a supermassive black hole are plausible at galactic centers. We present results from a numerical study of close to 13 million such encounters. Consistent with previous studies, we found that disrupted binaries produce bound extreme-mass-ratio binaries with eccentricities of $$\sim 0.97$$ which circularize dramatically by the time they enter the classical LISA sensitivity band. We also investigated the regions of parameter space for binary survival and estimated the distribution of orbital parameters post-encounter. Our results showed that the semi-major axis of the population of surviving binaries is not significantly affected by the encounter. On the other hand, the eccentricity does; it increases in most cases. As a consequence, the encounter with the super-massive black hole accelerates the merger of the surviving binary, increasing the predicted merger rates by up to $$1\%$$ .