Virtual talk only

Title: Hydrodynamical Evolution of Black-Hole Binaries Embedded in AGN Disks

Abstract: Stellar-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) disks are promising progenitors of black hole mergers detected in gravitational waves by LIGO/VIRGO. To better understand the hydrodynamical evolution of BBHs interacting with the disk gas, we perform a suite of high-resolution 2D simulations of binaries in local disk (shearing-box) models, considering various binary mass ratios, eccentricities and background disk properties. We adopt a robust post-processing treatment to evaluate the mass accretion rate, torque and energy transfer rate on the binary to determine its long-term orbital evolution. We find that circular comparable-mass binaries contract, with an orbital decay rate of a few times the mass doubling rate. In addition, our survey shows that less massive and wider binaries embedded in disks with a non-isothermal EOS and a low viscosity are easier to be hardened efficiently. Our findings demonstrate that the dynamics of BBHs embedded in AGN disks is quite different from that of isolated binaries in their own circumbinary disks. Furthermore, our results suggest that the hardening time-scales of the binaries are much shorter than their migration time-scales in the disk, for all reasonable binary and disk parameters.

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