Hydrodynamical evolution of black-hole binaries embedded in AGN discs

Stellar-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) discs are possible progenitors of black-hole mergers detected gravitational waves by LIGO/VIRGO. To better understand the hydrodynamical evolution BBHs interacting with disc gas, we perform a suite high-resolution 2D simulations binaries local (shearing-box) models, considering various mass ratios, eccentricities and background properties. We use $\gamma$-law equation state adopt robust post-processing treatment to evaluate accretion rate, torque energy transfer rate on determine its long-term orbital evolution. find that circular comparable-mass contract, an decay few times doubling rate. Eccentric always experience eccentricity damping. Prograde higher or smaller ratios generally have slower rates, some extreme cases exhibiting expansion. The averaged depends physical size accretor. flows highly variable, dominant variability frequency is apparent (in rotating frame around central massive BH) for but gradually shifts radial epicyclic as increases. Our findings demonstrate dynamics AGN quite different from isolated their own circumbinary discs. Furthermore, our results suggest hardening timescales much shorter than migration disc, all reasonable parameters.