AGN 盘 I 中二元-单体相互作用仿真：气体增强的二元轨道硬化

Stellar-mass binary black hole (BBH) 在 active galactic nuclei (AGN) 的吸积盘内的合并可能贡献于由 grounded-based GW detectors 检测到的引力波 (GW) 事件。特别是，BBH 与 single stellar-mass black hole (sBH) 之间的相互作用，称为 binary-single interaction (BSI) process，可能导致 detectable non-zero eccentricity 的 GW 事件。Previous studies of the BSI process, which neglected the effects of gas, showed that BSIs contribute non-negligibly to GW events in a coplanar disk environment。在本 work 中，我们进行一系列 2-dimensional hydrodynamical and N-body simulations to explore the BSI in a gas environment by coupling REBOUND with Athena++。我们进行 360 次 simulation runs，spanning parameters in disk surface density $\Sigma_0$ and impact parameter $b$。We find that the gas-induced energy dissipation within the three-body system becomes significant if the encounter velocity between the sBHs is sufficiently large ($\gg c_s$)。Our simulation results indicate that approximately half of the end states of the BSI are changed by gas。Furthermore, at higher gas density, the number of close encounters during the BSI process will increase and the end-state BBHs tend to be more compact。Consequently, the presence of gas may shorten the GW merger timescale for end-state BBHs and increase the three-body merger rate。