Oscillations of Innermost Region of Relativistic Accretion Disks

粗略地说，我们有两个主要的结果。首先是(1)相对论性吸积盘最内层是脉动不稳定的，当所谓的粘度α参数大于某个临界值时。二是(2)相对论性吸积盘最内层的单臂波为低频振荡，其频率与在低质量x射线双星中观测到的准周期振荡（QPO’s）频率相当。(1)相对论性吸积盘的最内层存在吸积流变为超音速的声速点。分析发现，当粘度较大时，声点区域是脉动不稳定的。随后，数值模拟证实了这一点。数值模拟进一步表明，振荡具有长期的变化。该调制周期与QPO的调制周期相当。(2)单臂波纹波是一种频率与QPO一样低的振荡模式。波纹波是圆盘在垂直于圆盘平面方向上的波浪振荡。我们进一步发现，在某些情况下，波纹波可以被困在相对论性吸积盘的最内层。这将有利于解释QPO。

Roughly speaking, we had two major results. The first is that (1)the innermost part of relativistic accretion disks is pulsationally unstable, when the so-called alpha-parameter of viscosity is larger than a critical value. The second is that(2) one-armed corrugation waves in the innermost part of relativistic accretion disks are low frequency oscillations whose frequencies are comparable with those of quasi-periodic oscillations (QPO's) observed in low mass X-ray binaries.(1)The innermost part of relativistic accretion disks has the sonic point where the accretion flow becomes supersonic. We found analytically that the sonic point region is pulsationally unstable when viscosity is large. Subsequently this was confirmed by numerical simulations. Numerical simulations show further that the oscillations have long term variations. This modulation period was found to be comparable with that of QPO'S.(2)As an oscillations mode whose frequency is as low as that of QPO's, we found one-armed corrugation waves. Corrugation waves are wavy oscillations of disks in the direction perpendicular to the disk plane. We found further that under some circumstances there corrugation waves can be trapped in the innermost part of relativistic accretion disks. This will be in favor of explaining QPO'S.