论文标题
不透明度驱动的对流和超级质量黑洞的积聚磁盘的变异性
Opacity Driven Convection and Variability in Accretion Disks around Supermassive Black Holes
论文作者
论文摘要
我们使用三维辐射磁力 - 流动力学模拟研究了径向范围内超质量黑洞周围的积聚盘的结构。对于活跃银河核（AGN）区域中的典型条件，Rosseland的平均不透明度预计将大于电子散射值。我们表明，铁不透明的凹凸会使磁盘变得不稳定。由于额外的湍流压力支持，对流产生的湍流会膨胀磁盘，并增强了局部角动量的运输。这也导致表面密度和磁盘加热的强烈波动。不透明度随温度升高和对流而降低。磁盘冷却，整个过程再次重复。这会导致磁盘尺度的高度和发光度变化的强大振荡在几年的时间范围内的$ \ 3-6美元以上。由于铁不透明度的颠簸将转移到具有不同质量和增生速率的黑洞的不同位置，因此我们建议这是一种物理机制，可以解释AGN的变异性，这些变异性在数十年的时间范围内具有广泛的幅度。
We study the structure of accretion disks around supermassive black holes in the radial range $30\sim 100$ gravitational radii, using a three dimensional radiation magneto-hydrodynamic simulation. For typical conditions in this region of Active Galactic Nuclei (AGN), the Rosseland mean opacity is expected to be larger than the electron scattering value. We show that the iron opacity bump causes the disk to be convective unstable. Turbulence generated by convection puffs up the disk due to additional turbulent pressure support and enhances the local angular momentum transport. This also results in strong fluctuations in surface density and heating of the disk. The opacity drops with increasing temperature and convection is suppressed. The disk cools down and the whole process repeats again. This causes strong oscillations of the disk scale height and luminosity variations by more than a factor of $\approx 3-6$ over a few years' timescale. Since the iron opacity bump will move to different locations of the disk for black holes with different masses and accretion rates, we suggest that this is a physical mechanism that can explain the variability of AGN with a wide range of amplitudes over a time scale of years to decades.
