New Analytical Insights Into Circumbinary Disk Dynamics

The study of gas disks surrounding a supermassive black-hole binary (SMBHB) and their evolution during both the inspiral and merger stages can inform electromagnetic searches for candidate SMBHBs, in addition to being relevant for the expected gravitational-wave signal. We describe a new analytical approach to the dynamics of circumbinary accretion disks, which draws from the study of test particle orbits in the restricted 3 body problem. The study aims to connect the stability of orbits in this picture to the dynamics of gas flows near the circumbinary gap and reconcile some of the results from full hydrodynamics simulations of these disks over different mass ratios and disk-binary inclinations. The results indicate a truncation of the central cavity at timescales shorter than the viscous timescale which has implications for the disk-binary interactions at all stages of the binary's evolution.