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arXiv 0905.3188astro-ph.HE
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康普顿厚超环面再处理机的X射线谱模型

An X-ray Spectral Model for Compton-Thick Toroidal Reprocessors

K. D. Murphy, T. Yaqoob

摘要:

1型和2型活动星系核的中心发动机被认为具有一个环形结构,可以吸收和再处理来自中心X射线源的高能光子。如果再处理器为康普顿厚度,则适用于直接拟合X射线数据的发射线和连续谱的计算具有挑战性,因为再处理后的发射取决于入射连续谱的光谱形状,这可能无法直接观察到。我们提出了新的Monte Carlo计算的格林函数的环形洗消机,提供了显着的改进,目前可用的模型。格林函数方法使得能够构建X射线光谱拟合模型,其允许任意入射光谱作为拟合过程的一部分。计算是完全相对论的,并已进行列密度,覆盖康普顿薄康普顿厚制度,入射光子能量高达500千电子伏。由于Fe Ka,Fe Kb和Ni Ka的再处理连续谱和荧光线发射被自洽地处理,消除了对目前常见的特设建模的需要。我们发现,在我们的环形几何的康普顿厚的反射光谱的软,硬X射线带的光谱形状是不同的相比,从磁盘模型。我们研究的一个关键结果是,一个康普顿厚的环形结构,对着相同的立体角在X射线源作为一个磁盘可以产生一个反射光谱,是6倍弱于从磁盘。这突出了所谓的“反射分数”作为立体角的广泛和错误的解释,从拟合盘反射模型获得康普顿厚源,而不考虑适当的几何考虑。(节录)

英文摘要:

The central engines of both type 1 and type 2 AGNs are thought to harbor a toroidal structure that absorbs and reprocesses high-energy photons from the central X-ray source. If the reprocessor is Compton-thick, the calculation of emission-line and continuum spectra that are suitable for direct fitting to X-ray data is challenging because the reprocessed emission depends on the spectral shape of the incident continuum, which may not be directly observable. We present new Monte-Carlo calculations of Green's functions for a toroidal reprocessor that provide significant improvements over currently available models. The Green's function approach enables the construction of X-ray spectral fitting models that allow arbitrary incident spectra as part of the fitting process. The calculations are fully relativistic and have been performed for column densities that cover the Compton-thin to Compton-thick regime, for incident photon energies up to 500 keV. The reprocessed continuum and fluorescent line emission due to Fe Ka, Fe Kb, and Ni Ka are treated self-consistently, eliminating the need for ad hoc modeling that is currently common practice. We find that the spectral shape of the Compton-thick reflection spectrum in both the soft and hard X-ray bands in our toroidal geometry is different compared to that obtained from disk models. A key result of our study is that a Compton-thick toroidal structure that subtends the same solid angle at the X-ray source as a disk can produce a reflection spectrum that is ~6 times weaker than that from a disk. This highlights the widespread and erroneous interpretation of the so-called "reflection-fraction" as a solid angle, obtained from fitting disk-reflection models to Compton-thick sources without regard for proper consideration of geometry. (Abridged)

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