A Spatial and Spectral Study of Nonthermal Filaments in Historical Supernova Remnants: Observational Results with Chandra
A Spatial and Spectral Study of Nonthermal Filaments in Historical Supernova Remnants: Observational Results with Chandra
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DOI：
10.1086/427620
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发表时间：
2004-11
期刊：
影响因子：
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通讯作者：
A. Bamba;R. Yamazaki;T. Yoshida;T. Terasawa;K. Koyama
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文献类型：
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作者：
A. Bamba;R. Yamazaki;T. Yoshida;T. Terasawa;K. Koyama
年轻超新星遗迹（SNRs）的外壳是高能电子最可能的加速点，具有扩散激波加速（DSA）机制。我们利用钱德拉的优异空间分辨率研究了四个历史信噪比（Cas A, Kepler's残余物，第谷残余物和RCW 86）中靠近激波锋面的空间和光谱特性。在所有的信噪比中，在信噪比的边缘发现了硬x射线辐射，这些辐射集中在非常狭窄的区域（所谓的细丝）；上游的视尺度宽度低于或在钱德拉点扩展函数的量级上，而它们为0。″5-40“（0.01-0.4 pc）在下游与最可靠的距离。这些细丝的光谱可以用热和非热（幂律和SRCUT）模型拟合。前者需要不现实的高温（约2 keV）和低丰度（约1太阳）才能从年轻的信噪比发射，因此不太可能。后者再现了最适合的光子指数为2.1-3.8或滚转频率为（0.1-28）× 1017 Hz的光谱，这让我们想起了通过DSA加速的电子的同步辐射。我们考虑了各种物理参数作为信噪比年龄的函数，包括之前在sn1006上的结果；下游长丝宽度随信噪比年龄增大，光谱变软，保持非热特征。我们还发现一个函数，即滚落频率除以下游尺度宽度的平方，与年龄呈负相关，这可能为我们提供一些关于DSA理论的信息。
The outer shells of young supernova remnants (SNRs) are the most plausible acceleration sites of high-energy electrons with the diffusive shock acceleration (DSA) mechanism. We studied spatial and spectral properties close to the shock fronts in four historical SNRs (Cas A, Kepler's remnant, Tycho's remnant, and RCW 86) with excellent spatial resolution of Chandra. In all of the SNRs, hard X-ray emissions were found on the rims of the SNRs, which concentrate in very narrow regions (so-called filaments); apparent scale widths on the upstream side are below or on the order of the point-spread function of Chandra, while they are 0.″5-40'' (0.01-0.4 pc) on the downstream side with most reliable distances. The spectra of these filaments can be fitted with both thermal and nonthermal (power law and SRCUT) models. The former requires unrealistic high temperature (≳2 keV) and low abundances (≲1 solar) for emission from young SNRs and may be thus unlikely. The latter reproduces the spectra with best-fit photon indices of 2.1-3.8, or roll-off frequencies of (0.1-28) × 1017 Hz, which reminds us of the synchrotron emission from electrons accelerated via DSA. We consider various physical parameters as functions of the SNR age, including the previous results on SN 1006; the filament width on the downstream side increases with the SNR age, and the spectrum becomes softer, keeping a nonthermal feature. It was also found that a function, that is, the roll-off frequency divided by the square of the scale width on the downstream side, shows negative correlation with the age, which might provide us some information on the DSA theory.