Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties
Study on the escape timescale of high-energy particles from supernova remnants through thermal X-ray properties
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DOI：
10.1093/pasj/psaa061
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发表时间：
2020-06
影响因子：
2.3
通讯作者：
Hiromasa Suzuki;A. Bamba;R. Yamazaki;Y. Ohira
中科院分区：
文献类型：
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作者：
Hiromasa Suzuki;A. Bamba;R. Yamazaki;Y. Ohira
在最近的十年里，对几个超新星遗迹（SNRs）的GeV/TeV伽马射线观测表明，加速粒子正在从它们的加速点逃逸。然而，它们何时以及如何逃离SNR附近还有待了解。最近的研究表明，粒子逃逸可能与热等离子体年龄的SNRs。我们提出了一个系统的研究粒子逃逸的时间演化，使用热X射线特性和伽马射线光谱使用38个SNR与GeV/TeV的伽马射线发射。我们使用指数截止幂律和破幂律模型对伽马射线谱进行了谱拟合，以估计指数截止或破能，这两者都是粒子逃逸的指标。在等离子体年龄的伽马射线截止/破裂能量的曲线图显示出类似的趋势，预测的分析/数值计算的条件下，冲击波是相互作用的薄星际介质或云的粒子逃逸。粒子逃逸的时间尺度估计为100 kyr从总能量的限制质子的等离子体年龄的下降趋势。在数据中的截止/破裂能量的大的分散体可能表明粒子逃逸环境的内在多样性。这可能是在地球上测量到的复杂的银河宇宙线光谱形状的原因。
In the current decade, GeV/TeV gamma-ray observations of several supernova remnants (SNRs) have implied that accelerated particles are escaping from their acceleration sites. However, when and how they escape from the SNR vicinities are yet to be understood. Recent studies have suggested that the particle escape might develop with thermal plasma ages of the SNRs. We present a systematic study on the time evolution of particle escape using thermal X-ray properties and gamma-ray spectra using 38 SNRs associated with GeV/TeV gamma-ray emissions. We conducted spectral fittings on the gamma-ray spectra using exponential cutoff power-law and broken power-law models to estimate the exponential cutoff or the break energies, both of which are indicators of particle escape. Plots of the gamma-ray cutoff/break energies over the plasma ages show similar tendencies to those predicted by analytical/numerical calculations of particle escape under conditions in which a shock is interacting with thin interstellar medium or clouds. The particle escape timescale is estimated as ∼100 kyr from the decreasing trends of the total energy of the confined protons with the plasma age. The large dispersions of the cutoff/break energies in the data may suggest an intrinsic variety of particle escape environments. This might be the cause of the complicated Galactic cosmic ray spectral shape measured on Earth.