Synchrotron X-ray diagnostics of cutoff shape of nonthermal electron spectrum at young supernova remnants
Synchrotron X-ray diagnostics of cutoff shape of nonthermal electron spectrum at young supernova remnants
复制标题
年轻超新星遗迹非热电子能谱截止形状的同步加速器 X 射线诊断
DOI：
10.1088/1674-4527/14/2/005
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发表时间：
2014
影响因子：
1.8
通讯作者：
Aya
中科院分区：
文献类型：
--
作者：
Yamazaki;Ryo ; Ohira;Yutaka ; Sawada;Makoto ; Bamba;Aya
同步加速器x射线是研究年轻超新星遗迹（SNRs）电子加速的有用工具。目前，由于信噪比激波周围的磁场构型是不确定的，电子加速是否受到信噪比年龄、同步加速器冷却、甚至逃离加速区域的限制尚不清楚。我们研究了电子能谱在最大能量附近的截止形状是否能约束加速机制。在最大电子能量由信噪比年龄、同步加速器冷却和逃离激波决定的每种情况下，我们推导出了截止形状的解析公式。它们与电子扩散系数的能量依赖性有关。接下来，我们讨论了在不久的将来是否可以通过观测提供有关截止形状的信息，这些信息将简单地给出软x射线和硬x射线波段的光子指数和通量比。我们发现，如果电子能谱的幂律指数是由其他观测独立确定的，那么我们可以通过将光子指数和/或通量比的理论预测与将由NuSTAR和/或ASTRO-H测量的观测数据进行比较来约束截止形状。这样的研究有助于理解加速机理。特别是，它将为信噪比冲击周围的磁场强度提供另一种独立的约束。
Synchrotron X-rays can be a useful tool to investigate electron acceleration at young supernova remnants (SNRs). At present, since the magnetic field configuration around the shocks of SNRs is uncertain, it is not clear whether electron acceleration is limited by SNR age, synchrotron cooling, or even escape from the acceleration region. We study whether the acceleration mechanism can be constrained by the cutoff shape of the electron spectrum around the maximum energy. We derive analytical formulae of the cutoff shape in each case where the maximum electron energy is determined by SNR age, synchrotron cooling and escape from the shock. They are related to the energy dependence of the electron diffusion coefficient. Next, we discuss whether information on the cutoff shape can be provided by observations in the near future which will simply give the photon indices and the flux ratios in the soft and hard X-ray bands. We find that if the power-law index of the electron spectrum is independently determined by other observations, then we can constrain the cutoff shape by comparing theoretical predictions of the photon indices and/or the flux ratios with observed data which will be measured by NuSTAR and/or ASTRO-H. Such study is helpful in understanding the acceleration mechanism. In particular, it will supply another independent constraint on the magnetic field strength around the shocks of SNRs.