标题： 塞弗特1型星系Ark 120的长期X射线观测：软谱段过量的起源 显示英文标题

标题： Long term X-Ray Observations of Seyfert 1 Galaxy Ark 120: On the origin of soft-excess

摘要： 我们对一个“裸型”AGN Ark 120进行了长期X射线光谱和时间分析。 我们考虑了从2003年到2018年XMM-Newton、Suzaku、Swift和NuSTAR的观测数据。 该源的光谱特性使用文献中各种现象模型和物理模型进行研究。 我们报告了（a）几个物理参数的变化，如电子云的温度和光学深度、康普顿云的大小以及过去十五年的吸积率。 光谱变化是从吸积动力学的变化来解释的；（b）在2003年，0.2-2 keV和3-10 keV光曲线之间的X射线时间延迟为零延迟，在2013年为正延迟4.71\pm 2.1 ks，在2014年为负延迟4.15\pm 1.5 ks。 延迟是通过康普顿化、反射和光行时来解释的；（c）使用nthcomp得到的长期固有光度，软过量和主连续谱显示出相关性，皮尔逊相关系数为0.922。 这表明软过量和主连续谱来源于同一物理过程。 从物理模型拟合中，我们推断Ark 120的软过量可能是康普顿云中少量散射的结果。 通过蒙特卡罗模拟，我们显示确实较少散射对应的光谱可以在0.2-3 keV范围内提供更陡的软过量幂律。 模拟的光度与观测值一致。 显示英文摘要

摘要： We present the long-term X-ray spectral and temporal analysis of a 'bare-type AGN' Ark 120. We consider the observations from XMM-Newton, Suzaku, Swift, and NuSTAR from 2003 to 2018. The spectral properties of this source are studied using various phenomenological and physical models present in the literature. We report (a) the variations of several physical parameters, such as the temperature and optical depth of the electron cloud, the size of the Compton cloud, and accretion rate for the last fifteen years. The spectral variations are explained from the change in the accretion dynamics; (b) the X-ray time delay between 0.2-2 keV and 3-10 keV light-curves exhibited zero-delay in 2003, positive delay of 4.71 \pm 2.1 ks in 2013, and negative delay of 4.15 \pm 1.5 ks in 2014. The delays are explained considering Comptonization, reflection, and light-crossing time; (c) the long term intrinsic luminosities obtained using nthcomp, of the soft-excess and the primary continuum show a correlation with a Pearson Correlation Coefficient of 0.922. This indicates that the soft-excess and the primary continuum are originated from the same physical process. From a physical model fitting, we infer that the soft excess for Ark 120 could be due to a small number of scatterings in the Compton cloud. Using Monte-Carlo simulations, we show that indeed the spectra corresponding to fewer scatterings could provide a steeper soft-excess power-law in the 0.2-3 keV range. Simulated luminosities are found to be in agreement with the observed values.