Accretion and emission processes in AGN
Accretion and emission processes in AGN
复制标题
AGN 中的吸积和发射过程
DOI：
10.1142/9789812811318_0005
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
S. Collin
中科院分区：
文献类型：
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作者：
S. Collin
紫外- x连续体、x射线光谱特征和这些波段的变异性为研究agn最内层区域提供了强有力的工具，从中我们可以了解吸积过程。在本章中，讨论的重点是发光AGN，即塞弗特星系和类星体。描述了标准吸积盘模型（一个静止的几何薄盘），并给出了径向结构的垂直平均解。用不同的近似方法讨论了标准圆盘的发射，并与观测结果进行了比较。由此得出结论，需要更复杂的模型，如辐射盘和盘-日冕模型。最后一个模型的优点是它解释了整个UV-X光谱分布。在这些圆盘模型的框架内，x射线铁谱线的轮廓、强度和变化特性可以通过在非常靠近黑洞的冷盘表面进行再处理来解释（“相对论圆盘模型”）。讨论了另一种可能性，其中UV-X连续体是由被热介质包围（或嵌入）的致密云的准球形分布产生的。在这样一个模型中，铁线的轮廓可能是由于复合效应而不是相对论效应。
The UV-X continuum, the X-ray spectral features, and the variability in these bands provide powerful tools for studying the innermost regions of AGNs from which we gain an insight into the accretion process. In this chapter the discussion focusses on luminous AGN, i.e. Seyfert galaxies and quasars. The standard accretion disk model (a stationary geometrically thin disk) is described, and vertically averaged solutions for the radial structure are given. The emission of the standard disk is discussed using different approximations, and it is compared to the observations. This leads to the conclusion that more complex models are required, such as the irradiated disk and the disk-corona models. The advantage of this last model is that it explains the overall UV-X spectral distribution. In the framework of these disk models, the profile, intensity, and variability properties of the X-ray iron line can be explained by reprocessing at the surface of the cold disk very close to the black hole (the "relativistic disk model"). An alternative possibility is discussed, where the UV-X continuum is produced by a quasi-spherical distribution of dense clouds surrounded by (or embedded in) a hot medium. In such a model the iron line profile could be due to Comptonization instead of relativistic effects.