Cosmic-ray diffusion near the Bohm limit in the Cassiopeia A supernova remnant
Cosmic-ray diffusion near the Bohm limit in the Cassiopeia A supernova remnant
复制标题
仙后座 A 超新星遗迹中接近玻姆极限的宇宙射线扩散
DOI：
10.1038/nphys391
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发表时间：
2006
期刊：
影响因子：
19.6
通讯作者：
J. Davis
中科院分区：
文献类型：
--
作者：
M. Stage;G. Allen;J. Houck;J. Davis
银河系中宇宙射线通过扩散激波(费米)加速的方式被认为主要发生在超新星遗迹(SNR)中。尽管有大量的理论工作，但确切的细节仍然未知，部分原因是很难直接观察到在SNR冲击中加速到TeV能量并影响其结构的核子。然而，在过去十年中，诸如ASCA(宇宙学和天体物理学高级卫星)以及最近的Chandra、XMM-牛顿和Suzaku等X射线观测站使人们能够成像在SNR冲击中加速的宇宙射线电子产生的kev级同步辐射。在这里，我们描述了银河系SNR仙后座A的钱德拉观测的空间分辨光谱分析，以绘制在前向激波中加速的电子的截止频率。我们设置扩散系数的上限，并找到粒子似乎以理论上可能的速度加速的位置(玻姆极限)。
The acceleration of cosmic rays in our Galaxy by means of diffusive shock (Fermi) acceleration is believed to occur primarily in supernova remnants (SNRs). Despite considerable theoretical work, the precise details are still unknown, in part because of the difficulty in directly observing nucleons that are accelerated to TeV energies in—and affect the structure of—SNR shocks. However, for the past ten years, X-ray observatories such as ASCA (Advanced Satellite for Cosmology and Astrophysics) and, more recently, Chandra, XMM-Newton and Suzaku, have made it possible to image the keV-scale synchrotron emission produced by cosmic-ray electrons accelerated in SNR shocks. Here, we describe a spatially resolved spectroscopic analysis of Chandra observations of the Galactic SNR Cassiopeia A to map the cutoff frequencies of electrons accelerated in the forward shock. We set upper limits on the diffusion coefficient and find locations where particles seem to be accelerated nearly as fast as theoretically possible (the Bohm limit).