X-Ray Fluctuations from Advection-dominated Accretion Disks with a Critical Behavior
X-Ray Fluctuations from Advection-dominated Accretion Disks with a Critical Behavior
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具有临界行为的平流主导吸积盘的 X 射线波动
DOI：
10.1086/304493
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
S. Mineshige
中科院分区：
文献类型：
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作者：
M. Takeuchi;S. Mineshige
提出了一种新的黑洞物体非周期性 X 射线波动的流体动力学模型。 X射线波动被认为源于黑洞周围吸积盘的不稳定性。我们之前提出了基于自组织临界性概念的元胞自动机模型来描述经历不稳定性的磁盘的开放、耗散性质。假设当质量密度超过某个临界值时就会触发雪崩，我们可以用这个模型重现 X 射线变异性的基本统计特征。作为一项独立调查，我们还计算了轴对称、平流主导的圆盘对热扰动的响应，证明它可以轻松产生 X 射线波动，如在 X 射线波动中观察到的那样。在本文中，我们将这两种不同的研究结合起来，并计算具有临界行为的平流主导盘的时间演化，即，如果表面密度超过某个临界值，我们让粘度增加。结果，我们成功地产生了类似 1/f 的波动。我们还发现波动特性取决于临界条件的规定。本模型预测功率谱密度 (PSD) 下降部分的斜率恒定，而分隔 PSD 平坦部分和下降部分的频率 fbreak 根据圆盘平流主导部分大小的变化而变化。
A new hydrodynamic model for aperiodic X-ray fluctuations from black hole objects is presented. X-ray fluctuation is thought to originate from instabilities of the accretion disk around a black hole. We previously proposed the cellular automaton model based on the notion of self-organized criticality to describe the open, dissipative nature of a disk undergoing instabilities. Assuming that an avalanche was triggered when the mass density exceeded some critical value, we could reproduce the basic statistical features of X-ray variability with this model. As an independent inquiry, we also calculated the response of an axisymmetric, advection-dominated disk to thermal perturbations, demonstrating that it can easily produce an X-ray shot as is observed in X-ray fluctuations. In this paper, we couple these two different lines of study and calculate the time evolution of an advection-dominated disk with a critical behavior, namely, if surface density exceeds some critical value, we let viscosity increase. As a result, we succeed in producing 1/f-like fluctuations. We also find that the fluctuation properties depend upon the prescription of the critical condition. The present model predicts a constant slope in the decline part of the power spectral density (PSD), while fbreak, the frequency separating the flat and decline parts of the PSD, changes according to variations in the size of the advection-dominated portions of the disk.