Dynamical pathways for stellar-mass black hole binary mergers and spin evolution, largely in the context of AGN disks around a supermassive black hole.
Black Hole Mergers through Evection Resonances
Existing pathways for speeding up stellar-mass black hole binary mergers usually need a strongly inclined outer perturber. This paper proposes a mechanism that instead works for near-coplanar systems: a black hole binary migrating through an AGN disk can be captured into an "evection" resonance, where the binary's own relativistic and disk-driven precession matches its orbital period around the central supermassive black hole. Capture into this resonance excites the binary's eccentricity, shortening the merger time by up to several orders of magnitude, with the effect strongest for more massive or more disk-embedded binaries.
Enhanced Blackhole Mergers in AGN Discs due to Precession-Induced Resonances
Building on the evection-resonance idea, this paper looks more broadly at precession-driven resonances between an intermediate-mass–stellar-mass black hole binary's nodal and apsidal precession and its orbital motion around a companion black hole. It derives where these resonances sit, how wide and how quickly a binary librates within them, and shows that a binary captured in one while slowly migrating can reach eccentricities as high as about 0.9, again substantially shortening the time to merger through gravitational-wave emission.
Secular Spin–Orbit Resonances of Black Hole Binaries in AGN Disks
The spin–orbit alignment of merging black hole binaries carries information about how they formed. This paper studies how a black hole's spin axis evolves inside a small circum-black-hole disk within a larger AGN disk, orbiting a supermassive black hole. A secular resonance between the black hole's spin precession and the binary's orbital precession can tip the spin into substantial misalignment with the orbit, producing a broad predicted range of spin–orbit misalignments and effective spins for these systems.
Additional co-authored work on black hole dynamics.