解决强场时空动力学和MHD对环双星盘物理的相对影响
Resolving the relative influence of strong field spacetime dynamics and MHD on circumbinary disk physics
摘要：
本文在相对论范围内研究了围绕超大质量黑洞双星的磁化和非磁化环双星吸积盘。我们使用后牛顿展开来构建一个解析时空，并确定后牛顿（PN）展开的顺序如何影响气体的动力学。我们发现非常小的差异，在晚时间的非磁化流体动力学演化的两个时空之间的整体动力学分离约$40GM/c^2$其中$M$是二进制的总质量。对于较小的分离，由于PN阶的差异变得可比的差异所造成的使用初始数据进一步从平衡。对于磁化气体，MHD应力，这驱动吸积动力学，往往掩盖所有高阶PN效应，甚至在分离的$20GM/c^2$，导致基本上相同的观察到的电磁光度。这意味着我们对EM信号的计算可能对小的二进制分离是鲁棒的。我们的调查是第一次展示PN精度的水平如何影响一个circumbinary磁盘的演变，并通知我们的范围内分离信任PN近似这种研究。我们还讨论了初始条件和二进制分离对模拟预测的影响。
英文摘要：
In this paper we evolve magnetized and unmagnetized circumbinary accretion disks around supermassive black hole binaries in the relativistic regime. We use a post-Newtonian expansion to construct an analytical spacetime and determine how the order of the post-Newtonian (PN) expansion affects the dynamics of the gas. We find very small differences in the late-time bulk dynamics of non-magnetized hydrodynamic evolutions between the two spacetimes down to separations of approximately $40GM/c^2$ where $M$ is the total mass of the binary. For smaller separations, the differences due to PN-order become comparable to differences caused by using initial data further from equilibrium. For magnetized gas, MHD stresses, which drives the accretion dynamics, tends to mask all higher order PN effects even at separations of $20GM/c^2$, leading to essentially the same observed electromagnetic luminosity. This implies that our calculations of the EM signal may be robust down to small binary separations. Our investigation is the first to demonstrate how the level of PN accuracy affects a circumbinary disk's evolution and informs us of the range in separation within which to trust the PN approximation for this kind of study. We also address the influence the initial conditions and binary separation have on simulation predictions.
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