从旋入到膨胀：气态介质中双星黑洞的尾流驱动扭矩
From Inspiral to Expansion: The Wake-Driven Torque on Binary Black Holes in Gaseous Medium
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中文总结 AI 辅助
该研究通过三维流体动力学模拟揭示气态介质中双星黑洞的尾流驱动扭矩由尾流相互作用及参数η控制，发现AGN盘中气体驱动膨胀可抑制其引力波旋入并合率。
中文摘要 AI 辅助
活跃星系核（AGN）盘等气态介质中的双星黑洞（BBH）是重要的引力波源，但支配其轨道演化的气体驱动扭矩仍未被完全理解。现有多数气体中BBH的研究常将净扭矩近似为每个黑洞受自身尾流施加的独立动力学摩擦（DF）力之和，忽略了两个尾流之间的相互引力耦合。我们对均匀流中的圆轨道BBH开展三维流体动力学模拟，发现扭矩由尾流-尾流相互作用决定。净扭矩由单一参数η≡v_g/v_o控制，即气体流速与双星轨道速度的比值。在小η时，尾流合并为单一过密包层，时间平均扭矩为负；随着η增大，尾流分离，扭矩变为正。在AGN盘中，盘模型中的并合通道双星自然产生处于正扭矩 regime 的η，膨胀时标与盘寿命相当或更短，表明气体驱动膨胀可与引力波旋入竞争，抑制并合通道的并合率。
英文摘要
Binary black holes (BBHs) in gaseous medium, such as active galactic nucleus (AGN) disks, are important gravitational-wave sources, yet the gas-driven torque that governs their orbital evolution remains to be fully understood. Most existing studies of BBHs in gas often approximate the net torque as the sum of independent dynamical friction (DF) forces exerted on each black hole by its own wake, neglecting the mutual gravitational coupling between the two wakes. We perform three-dimensional hydrodynamic simulations of circular BBHs in a uniform flow and find the torque is determined by the wake-wake interactions. The net torque is controlled by a single parameter $η\equiv v_g/v_o$, the ratio of the gas flow velocity to the binary orbital velocity. At small $η$, the wakes merge into a single overdense envelope and the time-averaged torque is negative; as $η$ increases, the wakes separate and the torque becomes positive. In AGN disks, capture-channel binaries in a disk model naturally produce $η$ in the positive-torque regime; the expansion timescale is comparable to or shorter than the disk lifetime, suggesting that gas-driven expansion can compete with gravitational-wave inspiral and suppress the capture-channel merger rate.
