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Accreting Binaries: From Brown Dwarfs to Major Mergers

Alexander Dittmann (Institute for Advanced Study) — November 3, 2025

Abstract

Accretion disks play important roles in the formation and evolution of binary systems, from stellar binaries within our own galaxy to the supermassive black hole binaries formed in the aftermath of galaxy mergers. The effects of a disk on its binary vary dramatically depending on the properties of each system, including any combination of causing binaries to either expand or shrink, and either circularizing binaries or driving them to higher eccentricities. I will review recent theoretical work on circumbinary accretion, with applications to the mass ratios and eccentricities of stellar binaries probed by Gaia, the types of black hole binaries in the disks of active galactic nuclei that might be probed by LIGO, and the supermassive black hole binaries probed by pulsar timing arrays and space-based interferometers.