We review recent works on the dynamics of circumbinary accretion, including time variability, angular momentum transfer between the disk and the binary, and the secular evolution of accreting binaries. These dynamics impact stellar binary formation/evolution, circumbinary planet formation/migration, and the evolution of (super)massive black hole binaries. We discuss the dynamics and evolution of inclined/warped circumbinary disks and connect with observations of protoplanetary disks. A special kind of circumbinary accretion involves binaries embedded in big disks, which may contribute to the mergers of stellar-mass black holes in AGN disks. Highlights include the following: ▪Circumbinary accretion is highly variable, being modulated at P b (the binary period) or ∼5P b, depending on the binary eccentricity e b and mass ratio q b.▪The inner region of the circumbinary disk can develop coherent eccentric structure, which may modulate the accretion and affect the physical processes (e.g., planet migration) taking place in the disk.▪Over long timescales, circumbinary accretion steers binaries toward equal masses, and it does not always lead to binary orbital decay. The secular orbital evolution depends on the binary parameters (e b and q b) and on the thermodynamic properties of the accreting gas.▪A misaligned disk around a low-eccentricity binary tends to evolve toward coplanarity due to viscous dissipation. But when e b is significant, the disk can evolve toward “polar alignment,” with the disk plane perpendicular to the binary plane.

中文翻译：

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外二星吸积：从双星到大质量双黑洞


我们回顾了最近关于环双星吸积动力学的工作，包括时间可变性、圆盘和双星之间的角动量转移，以及吸积双星的长期演变。这些动力学影响恒星双星的形成/演化、环双星行星的形成/迁移以及（超）大质量黑洞双星的演化。我们讨论了倾斜/翘曲的环二元盘的动力学和演化，并与原行星盘的观测结果相联系。一种特殊的环二星吸积涉及嵌入大盘中的双星，这可能导致 AGN 盘中恒星质量黑洞的合并。亮点包括以下内容： ▪环二星吸积是高度可变的，在 P b（双星周期）或 ∼5P b 处被调制，具体取决于双星偏心率 e b 和质量比 q b.▪环二星盘的内部区域可以发展出相干的偏心结构，这可能会调节吸积并影响盘▪中发生的物理过程（例如，行星迁移）。 环双星吸积将双星引导至相等质量，并且它并不总是导致双星轨道衰变。长期轨道演化取决于双星参数（e b 和 q b）和吸积气体的热力学性质.▪由于粘性耗散，围绕低偏心率双星的错位盘倾向于向共面演化。但是当 e b 显著时，圆盘可以向“极对齐”演化，磁盘平面垂直于双平面。