arXiv 1306.43312013-06-18astro-ph.SR

环双星盘中的波状翘曲传播I。解析理论与数值模拟

Wave-like warp propagation in circumbinary discs I. Analytic theory and numerical simulations

Stefano Facchini, Giuseppe Lodato, Daniel J. Price

备注：: 15 pages, 17 figures, accepted for publication in MNRAS
DOI：: 10.1093/mnras/stt877

摘要：

本文分析了原恒星环双星盘中翘曲的传播。我们使用这些系统作为一个测试环境中，研究弯曲波制度的翘曲传播，由于二进制引力势的外部扭矩的增加。特别是，我们要测试的线性政权，其中的分析理论已经开发。为了做到这一点，我们首先计算分析的稳态形状的无粘光盘的二进制扭矩。稳态倾斜是半径的单调递增函数。在没有粘性的情况下，盘不存在任何扭曲。然后，我们比较了通过已知的线性方程计算的翘曲盘的时间依赖性演化与解析解和全三维数值模拟，这已经与PHANTOM SPH代码使用200万个粒子进行。我们发现一个很好的协议，在倾斜和小倾角的相位演化，即使在非常低的粘度。此外，我们还验证了当α > H/R（α为圆盘粘性参数）时，线性化方程能够再现扩散行为。最后，我们使用3D模拟来探索非线性机制。我们观察到一个强烈的非线性行为，这导致了光盘的破碎。然后，内盘开始以它自己的旋进频率旋进。在围绕旋转黑洞的吸积盘中，已经通过数值模拟观察到了这种行为。星周吸积盘的演化强烈依赖于翘曲演化。因此，本文探讨的问题可能是至关重要的，以了解在拥挤的环境中的吸积盘的演变，当与其他恒星的引力相互作用是非常可能的，并在多个系统。

英文摘要：

In this paper we analyse the propagation of warps in protostellar circumbinary discs. We use these systems as a test environment in which to study warp propagation in the bending-wave regime, with the addition of an external torque due to the binary gravitational potential. In particular, we want to test the linear regime, for which an analytic theory has been developed. In order to do so, we first compute analytically the steady state shape of an inviscid disc subject to the binary torques. The steady state tilt is a monotonically increasing function of radius. In the absence of viscosity, the disc does not present any twist. Then, we compare the time-dependent evolution of the warped disc calculated via the known linearised equations both with the analytic solutions and with full 3D numerical simulations, which have been performed with the PHANTOM SPH code using 2 million particles. We find a good agreement both in the tilt and in the phase evolution for small inclinations, even at very low viscosities. Moreover, we have verified that the linearised equations are able to reproduce the diffusive behaviour when α > H/R, where α is the disc viscosity parameter. Finally, we have used the 3D simulations to explore the non-linear regime. We observe a strongly non-linear behaviour, which leads to the breaking of the disc. Then, the inner disc starts precessing with its own precessional frequency. This behaviour has already been observed with numerical simulations in accretion discs around spinning black holes. The evolution of circumstellar accretion discs strongly depends on the warp evolution. Therefore the issue explored in this paper could be of fundamental importance in order to understand the evolution of accretion discs in crowded environments, when the gravitational interaction with other stars is highly likely, and in multiple systems.

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英文摘要：

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