[论文解读] NuSTAR/XMM-Newton monitoring of the Seyfert 1 galaxy HE 1143-1810. Testing the two-corona scenario

F. Ursini, Pierre-Olivier Petrucci+12 more|arXiv (Cornell University)|Dec 17, 2019

Astrophysical Phenomena and Observations参考文献 92被引用 7

一句话总结

本研究利用HE 1143-1810星系中NuSTAR与XMM-Newton的同步观测，检验了双日冕模型，发现一个温日冕（kT ~ 0.5 keV，τ ~ 17–18）可解释软X射线过量，而位于约20个引力半径处、呈喷流发射盘（JED）几何构型的热日冕（kT ~ 20 keV，τ ~ 4）则产生硬X射线辐射。数据支持一种具有可变吸积率（0.7–0.9 L_Edd）的双相吸积流，与JED驱动的热日冕及覆盖外盘的温日冕一致。

ABSTRACT

We test the two-corona accretion scenario for active galactic nuclei in the case of the `bare' Seyfert 1 galaxy HE 1143-1810. We perform a detailed study of the broad-band UV--X-ray spectral properties and of the short-term variability. We present results of a joint XMM-Newton and NuSTAR monitoring of the source, consisting of 5x20 ks observations, each separated by 2 days, performed in December 2017. The source is variable in flux among the different observations, and a correlation is observed between the UV and X-ray emission. Moderate spectral variability is observed in the soft band. The time-averaged X-ray spectrum exhibits a cut-off at $\sim 100$ keV consistent with thermal Comptonization. We detect an iron K$α$ line consistent with being constant during the campaign and originating from a mildly ionized medium. The line is accompanied by a moderate, ionized reflection component. A soft excess is clearly present below 2 keV and is well described by thermal Comptonization in a `warm' corona with a temperature of $\sim 0.5$ keV and a Thomson optical depth of $\sim 17-18$. For the hot hard X-ray emitting corona, we obtain a temperature of $\sim 20$ keV and an optical depth of $\sim 4$ assuming a spherical geometry. A fit assuming a jet-emitting disc (JED) for the hot corona also provides a nice description of the broad-band spectrum. In this case, the data are consistent with an accretion rate varying between $\sim 0.7$ and $\sim 0.9$ in Eddington units and a transition between the outer standard disc and the inner JED at $\sim 20$ gravitational radii. The broad-band high-energy data agree with an accretion flow model consisting of two phases: an outer standard accretion disc with a warm upper layer, responsible for the optical--UV emission and the soft X-ray excess, and an inner slim JED playing the role of a hard X-ray emitting hot corona.

研究动机与目标

• 检验'裸露'型赛弗特1型星系HE 1143-1810中的双日冕吸积情景。
• 确定源中软X射线过量和硬X射线辐射的物理起源。
• 探究喷流发射盘（JED）几何构型是否可解释其全波段X射线谱与变异性。
• 约束吸积率及标准吸积盘（SAD）与JED相变之间的过渡半径。

提出的方法

• 开展了为期5个周期的XMM-Newton与NuSTAR同步监测，每次观测持续约20 ks，周期间隔为2天。
• 对能量范围从~0.3 keV至~100 keV的全波段紫外–X射线谱进行了分析。
• 使用包含温日冕与热日冕热Compton化物理模型，拟合时间平均谱与单次观测谱。
• 对热日冕测试了喷流发射盘（JED）模型，假设相变半径位于~20个引力半径处。
• 采用SAD–JED模型描述吸积流，自由参数为吸积率与相变半径。
• 应用射电喷流功率关系（νLν ∝ ṁ^{17/12} r_in (r_J - r_in)^{5/6}），估算喷流效率因子f̃_R。

实验结果

研究问题

• RQ1 HE 1143-1810中的软X射线过量是否源自温日冕中的热Compton化？
• RQ2 硬X射线辐射与高能截止（~100 keV）是否可由JED几何构型下的热日冕解释？
• RQ3 观测到的通量变异性是否由吸积率变化引起，且是否与JED模型一致？
• RQ4 在~20 R_G处的SAD–JED相变是否能为全波段谱提供物理解释？
• RQ5 在推断的吸积率与相变半径下，观测到的射电辐射是否与JED驱动的喷流一致？

主要发现

• 软X射线过量最适宜由温日冕中的热Compton化解释，其温度约为~0.5 keV，汤姆孙光学深度约为~17–18。
• 硬X射线辐射与假设球对称几何构型下的热日冕（~20 keV，光学深度~4）一致。
• JED模型对全波段谱拟合极佳，吸积率在~0.7至~0.9 L_Edd之间变化。
• 标准吸积盘与JED之间的相变半径被约束在~20个引力半径，波动极小（~10%）。
• 射电喷流功率关系得出无量纲因子f̃_R ~ 1.3×10⁻⁹，与X射线双星（如GX 339-4）中的值相近。
• 铁Kα线较窄，且保持恒定，起源于弱电离介质，具有中等程度的电离反射成分。