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arXiv 2008.12381astro-ph.HE
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Lense-Thirring旋进错位椎间盘I

Lense-Thirring Precession of Misaligned Discs I

Sergei Dyda, Christopher S. Reynolds

摘要:

利用动量方程中的重磁项,研究了无粘和粘滞两种非对准$α-$盘在黑洞周围的Lense-Thirring进动。对于弱未对准$i \lesssim 10^{\circ}$,盘表现得像刚体,经历全套经典谐振子动力学,包括弱和临界阻尼运动(由于粘性)、进动(由于Lense-Thirring扭矩)和章动(由于拱点进动)。对于强烈的错位,$i \gtrsim 30^{\circ}$,我们发现足够薄,$h/r \lesssim 0.05$光盘打破,形成一个缺口和内部和外部的子光盘发展准独立地从缓慢的传质。假设声速设定了盘中翘曲的传播速度,我们可以通过要求内子盘像刚体一样进动来估计断裂半径。我们明确地表明,第一次使用网格代码,爱因斯坦潜力是需要再现的内部光盘边缘的分析性质,并找到光盘打破。在大倾角,我们发现多个光盘断裂,与最近的GRMHD模拟高度倾斜的光盘。我们的研究结果表明,包括一个重磁项和适当的伪牛顿势捕获的重要定量特征的错位光盘。

英文摘要:

We study Lense-Thirring precession of inviscid and viscous misaligned $α-$discs around a black hole using a gravitomagnetic term in the momentum equation. For weak misalignments, $i \lesssim 10^{\circ}$, the discs behave like rigid bodies, undergoing the full suite of classical harmonic oscillator dynamics including, weak and critically damped motion (due to viscosity), precession (due to Lense-Thirring torque) and nutation (due to apsidal precession). For strong misalignments, $i \gtrsim 30^{\circ}$, we find sufficiently thin, $h/r \lesssim 0.05$ discs break, form a gap and the inner and outer sub-discs evolve quasi independently apart from slow mass transfer. Assuming the sound speed sets the communication speed of warps in the disc, we can estimate the breaking radius by requiring that the inner sub-disc precesses like a rigid body. We explicitly show for the first time using a grid code that an Einstein potential is needed to reproduce the analytic properties of the inner disc edge and find disc breaking. At large inclination angles we find multiple disc breaks, consistent with recent GRMHD simulations of highly inclined discs. Our results suggest that the inclusion of a gravitomagnetic term and appropriate pseudo-Newtonian potential captures the important quantitative features of misaligned discs.

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