Studies of emission regions of the X-ray pulsar Hercules X-1 with pulse-phase-resolved spectra observed with Suzaku
Studies of emission regions of the X-ray pulsar Hercules X-1 with pulse-phase-resolved spectra observed with Suzaku
复制标题
利用朱雀观测到的脉冲相位分辨光谱研究 X 射线脉冲星 Hercules X-1 的发射区域
DOI：
10.1093/pasj/psaa120
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发表时间：
2021
影响因子：
2.3
通讯作者：
Hajime Inoue
中科院分区：
文献类型：
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作者：
Keisuke Kondo;Tadayasu Dotani;Hajime Inoue
分析了用朱雀观测到的 X 射线脉冲星 Her X-1 的脉冲相位分辨 X 射线光谱。该分析基于这样的假设：观察到的与中子星自旋相关的连续光谱的变化源于从观察者处观察到的发射区域的投影面积的变化，并且从每个发射区域观察到的光谱形状不随视角变化而改变。我们计算整个能量范围内任意脉冲相位分辨光谱对之间每个能量仓中的通量比率。我们在这些比率光谱中识别出平坦部分，这可能表明在~1 keV以下、2-6 keV和高于~18 keV的三个能带中具有不变光谱形状的本征发射成分。然后，我们从一对显示比率谱中平坦部分的相位分辨光谱中近似求解本征光谱分量的联立方程。结果，获得三个成分的光谱作为与平坦部分对应的低能带、中能带和高能带。研究发现它们分别与软黑体模型、截止幂律模型和硬黑体模型非常吻合。最后，我们将所有相位分辨光谱同时与三个连续成分以及回旋吸收特征和铁线的复合模型进行拟合，并获得了可接受的结果。结合最近开发的理论模型讨论了截止幂律和硬黑体分量的起源。
Pulse-phase-resolved X-ray spectra of the X-ray pulsar Her X-1 observed with Suzaku are analyzed. The analysis is based on a hypothesis that the observed variations of the continuum spectra associated with the neutron star spin originate in the changes of the projection areas of the emission regions viewed from the observer, and that the spectral shape observed from each of the emission regions does not change with the viewing angle variation. We calculate the ratios of the fluxes in each energy bin between arbitrary pairs of the pulse-phase-resolved spectra over the entire energy range. We identify flat portions in these ratio spectra, which are likely to indicate the intrinsic emission components that have invariant spectral shapes, in the three energy bands of below ∼1 keV, 2–6 keV, and above ∼18 keV. Then, we approximately solve the simultaneous equations for the intrinsic spectral components from a pair of the phase-resolved spectra that show flat portions in the ratio spectrum. As a result, spectra of the three components are obtained as the low-, medium-, and high-energy bands corresponding to those for the flat portions. They are found to be well fitted with a soft blackbody, a cut-off power law, and a hard blackbody model, respectively. Finally, we fit all the phase-resolved spectra simultaneously with a composite model of three continuum components together with a cyclotron absorption feature and an iron line, and obtain an acceptable result. The origins of the cut-off power-law and hard blackbody components are discussed in relation to recently developed theoretical models.