The Effect of Star--Disk Interactions on Highly Eccentric Stellar Orbits in Active Galactic Nuclei: A Disk Loss Cone and Implications for Stellar Tidal Disruption Events
Galactic center black holes appear to be nearly universally surrounded by dense stellar clusters. When these black holes go through an active accretion phase, the multiple components of the accretion disk, stellar cluster, and black hole system all coexist. We analyze the effect of drag forces on highly eccentric stellar orbits incurred as stars puncture through the disk plane. Disk crossings dissipate orbital energy, drawing eccentric stars into more circular orbits. For high surface density disks, such as those found around black holes accreting near the Eddington mass accretion limit, the magnitude of this energy dissipation can be larger than the mean scatterings that stars receive by two body relaxation. One implication of this is the presence of a disk "loss cone" for highly eccentric stellar orbits where the dissipation from disk interaction outweighs scatter via two body relaxation. The disk loss cone is larger than the tidal disruption loss cone for near-Eddington black hole accretion rates. Stellar orbits within the disk loss cone are lost from the overall cluster as stellar orbits are circularized and stars are potentially ablated by their high-velocity impacts with the disk. We find, however, that the presence of the disk loss cone has a minimal effect on the overall rate of stellar tidal disruptions. Stars are still efficiently fed to the black hole from more-distant stellar orbits that receive large-enough per orbit scatter to jump over the disk loss cone and end up tidally disrupted.
Tidal disruptions of main sequence stars -- III. Stellar mass dependence of the character of partial disruptions
本文是这一系列研究的第三篇，我们继续研究非旋转$10^{6}~\rm{M}_\odot$超大质量黑洞对主序星的潮汐扰动事件。在这里，我们专注于恒星质量依赖的部分中断的结果。随着碰撞的减弱，碎片质量越来越集中在能量分布的外缘附近。结果，质量回退率可以实质上偏离$t^{-5/3}$幂律，变得更像具有尾部的单峰，如$t^{-p}$与$p\simeq2-5$。幸存的残余物在赤道方向旋转，比相同质量的主序星更热。它们的比轨道能量是碎片的$\simeq10^{-3}\times$，但相对于黑洞势，它们的比角动量接近原始恒星的比角动量。即使是强烈的碰撞，残余物的速度相对于黑洞势$\lesssim 300$ km s $^{-1}$也是无穷大的，所以它们不能走得很远进入银河系凸起。与黑洞结合最深的残余物在第一次返回近心时经历了第二次潮汐破裂事件;如果它们没有热弛豫，它们将完全破裂。
Tidal Disruptions of White Dwarfs: Theoretical Models and Observational Prospects
进入黑洞潮汐半径的质量为$\lesssim$ $10^5$ M $_{\odot}$的白矮星注定会被潮汐力撕裂。在恒星黑洞和超大质量黑洞之间的这个质量范围内的黑洞还没有被最终确定，所以检测到白矮星的潮汐破裂将为中等质量黑洞的存在提供明确的证据。在这篇综述中，我们提出了一个理论和观测的瞬态事件，导致从白矮星的潮汐中断的中等质量黑洞。这包括讨论最新的模拟和预测的属性，观测搜索的结果，以及总结潜在的引力波发射将被检测与即将到来的任务。
