热电子与非热电子产生的逆康普顿散射的X射线偏振
X-ray Polarization of Inverse Compton Scattering by Thermal and Nonthermal Electrons
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中文总结 AI 辅助
本研究通过数值模拟与半解析计算，分析热、非热及混合电子群的逆康普顿散射X射线偏振特性，证实X射线偏振测量可用于诊断吸积驱动系统的电子能量分布。
中文摘要 AI 辅助
来自吸积驱动天体物理系统的X射线辐射被广泛认为是高能电子与软光子之间的逆康普顿（IC）散射产生的。除了辐射强度外，这种辐射的偏振还能提供有关所涉及电子物理性质的重要信息。我们研究不同电子群如何塑造X射线波段IC辐射的能谱和偏振。我们考虑三种电子群：纯热电子、纯非热幂律电子以及结合两种成分的混合电子群。我们同时采用数值模拟和半解析计算方法，首先分别研究热电子和非热电子的情况，随后聚焦于在高能天体环境中被认为更符合实际的混合电子群。对于混合电子群，散射辐射分为三个能量区域：低能区（≤0.1 keV）由热电子主导，高能区（≥4 keV）由非热成分主导，在这两个极限之间存在约0.1-4 keV的过渡带，两种成分均有贡献。偏振度在这些区域之间平滑变化，过渡带的行为直接反映了热电子与非热电子的相对重要性。我们进一步表明，对于部分偏振的种子光子，散射后的偏振与入射偏振呈线性比例关系，且其频率依赖关系保持不变。这些结果表明，X射线偏振测量为吸积驱动系统中的电子能量分布提供了有力的诊断手段。
英文摘要
X-ray emission from accretion-powered astrophysical systems is widely interpreted as inverse Compton (IC) scattering between energetic electrons and soft photons. Besides the emitted intensity, the polarization of this radiation provides important information about the physical properties of the electrons involved. We investigate how different electron populations shape both the spectrum and polarization of IC emission in the X-ray band. We consider three electron populations: purely thermal, purely nonthermal power-law, and a hybrid population combining both components. We take both numerical simulations and semi-analytic calculations. We first attempt the cases for thermal and nonthermal electrons, respectively. We then focus on the hybrid population, which is expected to be realistic in high-energy object environments. For the case of hybrid electrons, the scattered emission separates into three energy regimes. At low energies ($\lesssim 0.1$ keV), it is dominated by thermal electrons; at high energies ($\gtrsim 4$ keV), it is governed by the nonthermal component. Between these limits, a transition band ($\sim 0.1$-$4$ keV) appears in which both components contribute. The degree of polarization varies smoothly across these regimes, and the behavior in the transition band directly traces the relative importance of thermal and nonthermal electrons. We further show that for partially polarized seed photons, the scattered polarization scales linearly with the incident polarization while its frequency dependence remains unchanged. These results show that X-ray polarimetry provides a powerful diagnostic of the electron energy distribution in accretion-powered systems.
