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arXiv 1909.07559astro-ph.HE
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具有辐射驱动外流的细长吸积盘的整体解

A global solution to a slim accretion disk with radiation-driven outflows

Junjie Feng, Xinwu Cao, Wei-Min Gu, Ren-Yi Ma

摘要:

薄盘的厚度取决于辐射力与黑洞重力垂直分量之间的平衡。结果表明,垂直重力随圆盘高度的增加而增加,当圆盘厚度超过某一临界值时,垂直重力随圆盘高度的增加而减小,这意味着当圆盘厚度超过某一临界值时,圆盘表面的气体可能被辐射力驱入外流.在这项工作中,我们得到了一个全球性的解决方案,一个薄盘辐射驱动的外流。我们发现,当吸积率$\dot{m} \gtrsim 1.78-1.91$($\dot{m}=\dot{M}/\dot{M}_{\rm Edd}$,和$\dot{M}_{\rm Edd}=L_{\rm Edd}/0.1c^2$)依赖于BH质量时,盘表面的外流被驱动,而当吸积率低于这个临界值时,盘表面的外流被抑制.质量吸积率随着半径的减小而减小,即使盘外缘的质量吸积率非常高,BH吞噬的气体的速率也总是限制在$\dot{m}_{\rm in}\sim 1.78-1.91$。这可能会限制早期宇宙中通过吸积而产生的大规模BH增长。由于外流的存在,有一个上限的辐射通量的磁盘,这导致饱和的连续光谱的磁盘在高能量带的外流。这可以通过类星体或/和BH X射线双星的观测来检验。

英文摘要:

The thickness of a slim disk is determined by the balance between the radiation force and the vertical component of the gravity of the black hole (BH). It was found that vertical gravity increases with the disk height, and it will decrease with the disk height if the disk thickness is above a critical value, which implies that gas at the disk surface may be driven into outflows by radiation force when the disk thickness surpasses the critical value. In this work, we derive a global solution to a slim disk with radiation-driven outflows. We find that the outflows are driven from the disk surface if the mass accretion rate $\dot{m} \gtrsim 1.78-1.91$ ($\dot{m}=\dot{M}/\dot{M}_{\rm Edd}$, and $\dot{M}_{\rm Edd}=L_{\rm Edd}/0.1c^2$) depending on BH mass, while the outflows are suppressed when the mass accretion rate is lower than this critical value. The mass accretion rate decreases with decreasing radius in the disk with outflows, and the rate of the gas swallowed by the BH is always limited to $\dot{m}_{\rm in}\sim 1.78-1.91$ even if the mass accretion rate at the outer edge of the disk is very high. This may set constraints on the massive BH growth through accretion in the early Universe. Due to the presence of outflows, there is an upper limit on the radiation flux of the disk, which leads to saturation of the continuum spectra of the disk with outflows at the high energy band. This may be tested by the observations of quasars or/and BH X-ray binaries.

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