Simple interpretation of the seemingly complicated X-ray spectral variation of NGC 5548
Simple interpretation of the seemingly complicated X-ray spectral variation of NGC 5548
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简单解读NGC 5548看似复杂的X射线光谱变化
DOI：
10.1093/mnras/stac1206
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发表时间：
2022
影响因子：
4.8
通讯作者：
Yasuharu Sugawara
中科院分区：
文献类型：
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作者：
Takuya Midooka;Ken Ebisawa;Misaki Mizumoto;Yasuharu Sugawara
NGC 5548是一个在宽波长范围内被研究得很好的塞弗特1星系。以前的多波长观测活动表明，它的多个吸收体是高度可变和复杂的。以前的研究应用了两个区域的部分覆盖模型与不同的覆盖分数来解释复杂的X射线光谱变化，并报告了一个覆盖分数和光子指数的幂律连续体之间的相关性。然而，从物理上理解这种相关性并不简单。在本文中，我们提出了一个模型，以避免这种非物理的情况下，中心的X射线发射区部分覆盖的cluronium吸收剂组成的双层。这些“双重部分覆盖”具有完全相同的覆盖分数。基于我们的模型，我们利用XMM-Newton，Suzaku和NuSTAR在0.3-78 keV范围内16年的数据进行了广泛的光谱研究。因此，我们发现，X射线光谱的变化主要是由以下三个分量的独立变化来解释的：（1）低于10.1 keV的软过剩光谱分量，（2）截止幂律归一化，（3）部分覆盖率的cloudrons吸收。特别是，光谱变化以上的1001千电子伏的部分覆盖分数和幂律归一化的变化，主要是解释。相反，光子指数和所有其他光谱参数没有显着变化。
NGC 5548 is a very well-studied Seyfert 1 galaxy in broad wavelengths. Previous multiwavelength observation campaigns have indicated that its multiple absorbers are highly variable and complex. A previous study applied a two-zone partial covering model with different covering fractions to explain the complex X-ray spectral variation and reported a correlation between one of the covering fractions and the photon index of the power-law continuum. However, it is not straightforward to physically understand such a correlation. In this paper, we propose a model to avoid this unphysical situation; the central X-ray emission region is partially covered by clumpy absorbers composed of double layers. These ‘double partial coverings’ have precisely the same covering fraction. Based on our model, we have conducted an extensive spectral study using the data taken byXMM–Newton,Suzaku, andNuSTARin the range of 0.3–78 keV for 16 yr. Consequently, we have found that the X-ray spectral variations are mainly explained by independent changes of the following three components; (1) the soft excess spectral component below ∼1 keV, (2) the cut-off power-law normalization, and (3) the partial covering fraction of the clumpy absorbers. In particular, spectral variations above ∼1 keV are mostly explained only by the changes of the partial covering fraction and the power-law normalization. In contrast, the photon index and all the other spectral parameters are not significantly variable.