标题： 薄吸积盘广义相对论磁流体力学模拟中的盘撕裂导致低频和高频拟周期振荡 显示英文标题

标题： Disk Tearing Leads to Low and High Frequency Quasi Periodic Oscillations in a GRMHD Simulation of a Thin Accretion Disk

摘要： 黑洞X射线双星（BHXRBs）表现出各种各样的变化现象，从长时间的光谱态变化到短期的宽带变化和准周期振荡（QPOs）。 一个特别令人困惑的方面是QPOs的产生，如果能够正确理解，它们可以作为黑洞吸积和演化的强大诊断工具。 在这项工作中，我们分析了一个高分辨率的三维广义相对论磁流体力学模拟，该模拟中的几何薄吸积盘相对于黑洞自转轴倾斜了$65^{\circ}$。 我们发现，快速旋转的10$M_\odot$黑洞产生的拉姆斯-瑟林扭矩导致几个子盘在$\sim 10-20$个引力半径内撕裂开。 撕裂以秒级的时间尺度循环发生。 在每次撕裂循环中，内子盘在落入黑洞之前会进动1至5个周期。 我们发现进动频率为$\sim 3\rm Hz$，与观测到的低频QPOs一致。 此外，在内盘质量加权半径的功率谱中，我们还发现了一个中心频率为$\sim55$Hz 的高频QPO（HFQPO）。 这个信号是由位于撕裂半径处的一圈气体的径向环状振荡引起的，这强烈表明X射线光变曲线也会有相应的调制，因此可能解释了一些观测到的高频QPOs。 显示英文摘要

摘要： Black hole X-ray binaries (BHXRBs) display a wide range of variability phenomena, from long duration spectral state changes to short-term broadband variability and quasi-periodic oscillations (QPOs). A particularly puzzling aspect is the production of QPOs, which -- if properly understood -- could be used as a powerful diagnostic tool of black hole accretion and evolution. In this work we analyse a high resolution three-dimensional general relativistic magnetohydrodynamic simulation of a geometrically thin accretion disk which is tilted by $65^{\circ}$ with respect to the black hole spin axis. We find that the Lense-Thirring torque from the rapidly spinning 10 $M_\odot$ black hole causes several sub-disks to tear off within $\sim 10-20$ gravitational radii. Tearing occurs in cycles on timescales of seconds. During each tearing cycle the inner sub-disk precesses for 1-5 periods before it falls into the black hole. We find a precession frequency of $\sim 3\rm Hz$, consistent with observed low-frequency QPOs. In addition, we find a high frequency QPO (HFQPO) with centroid frequency of $\sim55$Hz in the power spectra of the mass-weighted radius of the inner disk. This signal is caused by radial epicyclic oscillations of a dense ring of gas at the tearing radius, which strongly suggests a corresponding modulation of the X-ray lightcurve and may thus explain some of the observed HFQPOs.