Abstract—The properties of X-ray emission of the active nucleus of the Seyfert 2 galaxy NGC 7172 detected by the NuSTAR space observatory in 2014 are analyzed. This source exhibits constant obscuration N_H ≈ 8 × 10²² cm^–2, which is similar to that determined by XMM-Newton, Suzaku, ASCA, and BeppoSAX in the past 30 years. Spectral analysis reveals the presence of a moderate reflection component with \(\left\langle R \right\rangle \) = 0.44 and a narrow FeK_α line with EW = \(67_{{ - 14}}^{{ + 13}}\) eV. Numerical torus models confirm that the Seyfert nucleus of NGC 7172 is of a Compton-thin type and provide estimates of the torus inclination (Θ_i ≈ 61° and its opening angle (Θ_t ≈ 59°). The data of earlier observations reveal approximately order-of-magnitude variations of intrinsic luminosity L_intr(2–10 keV) and fourfold variations of equivalent width EW FeK_α on a timescale of 12 years, which corresponds to distance d ≈ 3.7 pc. This behavior of L_intr(2–10 keV) is indicative of variability of the central source. The results of spectral analysis, the lag between variations of the intrinsic luminosity and EWFeK_α, and the variation of intensity \({{I}_{{{\text{Fe}}{{K}_{\alpha }}}}}\) agree best with the scenario of production of the observed FeK_α line in a distant gas-dust torus.

中文翻译：

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NuSTAR观察到NGC 7172的活动核模糊

摘要—分析了2014年NuSTAR空间观测站检测到的Seyfert 2星系NGC 7172的活动核的X射线发射特性。此源表现出恒定的遮蔽Ñ _ħ ≈8×10 ²²厘米^-2，这是类似于由XMM牛顿，朱雀，ASCA和BeppoSAX号在过去30年来确定。频谱分析揭示了一个适度的反射分量与存在\（\左\ langle r \右\ rangle \） = 0.44和窄的Fe ķ _α与线EW = \（67 _ {{ - 14}} ^ {{+ 13 }} \）eV。数值圆环模型确认NGC 7172的赛弗特核是康普顿薄型的，并且提供环面倾角的估计（Θ_我≈61°和其开口角度（Θ_吨≈59°），早期观察的数据揭示了大约固有光度的顺序的数量级变化大号_INTR（2-10千电子伏）和等效宽度的四倍变化EW的Fe ķ _α上的12年的时间尺度，其对应于距离d ≈3.7的PC。此行为大号_INTR（2 –10 keV）表示中心光源的可变性，光谱分析的结果，固有光度变化与EW的Fe ķ _α，和强度的变化\（{{I} _ {{{\文本{铁}} {{K} _ {\阿尔法}}}}} \）同意最好与生产的场景观察到的Fe ķ _α在一个遥远的气尘环面线。