Massive black hole binary eccentricity in rotating stellar systems
Massive black hole binary eccentricity in rotating stellar systems
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DOI：
10.1111/j.1745-3933.2011.01073.x
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发表时间：
2011-05
影响因子：
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通讯作者：
A. Sesana;A. Gualandris;M. Dotti
中科院分区：
文献类型：
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作者：
A. Sesana;A. Gualandris;M. Dotti
本文研究了嵌入旋转恒星尖点的大质量黑洞双星的偏心率演化。在观测到反向旋转（相对于MBHB）轨道上的恒星比同向旋转的恒星更有效地从双星中提取角动量之后，MBHB的偏心率演化必须取决于周围恒星分布的同向旋转（反向旋转）程度。使用一个混合方案，耦合数值三体散射的尖点二进制相互作用的分析形式主义，我们验证了这一假设，通过不断发展的MBHB球对称尖点与不同的分数F的共同旋转的恒星。与以前的工作相一致，在各向同性尖点（F=0.5）的二进制倾向于增加其偏心率，当F接近零（反向旋转尖点）的偏心率迅速增加到几乎为1。相反地，具有显著共旋度（F>0.7）的尖点双星倾向于变得越来越不偏心，当F接近1时，圆化速度相当快。直接N体积分进行测试的理论，证实的混合计划的结果，至少在定性水平。我们讨论定量的差异，归因于其起源的混合方法的过度简化的性质。
In this letter we study the eccentricity evolution of a massive black hole (MBH) binary (MBHB) embedded in a rotating stellar cusp. Following the observation that stars on counter-rotating (with respect to the MBHB) orbits extract angular momentum from the binary more efficiently then their co-rotating counterparts, the eccentricity evolution of the MBHB must depend on the degree of co-rotation (counter-rotation) of the surrounding stellar distribution. Using an hybrid scheme that couples numerical three-body scatterings to an analytical formalism for the cusp-binary interaction, we verify this hypothesis by evolving the MBHB in spherically symmetric cusps with different fractions F of co-rotating stars. Consistently with previous works, binaries in isotropic cusps (F=0.5) tend to increase their eccentricity, and when F approaches zero (counter-rotating cusps) the eccentricity rapidly increases to almost unity. Conversely, binaries in cusps with a significant degree of co-rotation (F>0.7) tend to become less and less eccentric, circularising quite quickly for F approaching unity. Direct N-body integrations performed to test the theory, corroborate the results of the hybrid scheme, at least at a qualitative level. We discuss quantitative differences, ascribing their origin to the oversimplified nature of the hybrid approach.