Spectra of accelerated particles at supernova shocks in the presence of neutral hydrogen: the case of Tycho
Spectra of accelerated particles at supernova shocks in the presence of neutral hydrogen: the case of Tycho
复制标题
中性氢存在下超新星激波加速粒子的光谱：第谷的情况
DOI：
10.1051/0004-6361/201527761
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
P. Blasi
中科院分区：
文献类型：
--
作者：
G. Morlino;P. Blasi
激波附近中性氢的存在改变了激波的结构，影响了通过一阶费米机制加速的粒子谱。这一现象对解释超新星残余物辐射的多频光谱具有深远的意义。中性物质与激波下游的热离子进行电荷交换，可能导致快速中性物质向上游气体移动，在那里它们可能遭受额外的电荷交换或电离反应，从而在上游沉积能量和动量。在这里，我们讨论了这种中性返回通量的含义，这已经在我们之前的工作中预测了中性介导的超新星激波，并展示了加速粒子的光谱如何明显地比p^{-4}$陡峭，从而影响了超新星遗迹的伽马射线光谱，特别是第谷。描述中性氢存在下的非线性扩散激波加速度的理论是近年来发展起来的。在这里，我们使用了在以前的工作中发展起来的半分析理论，并将我们的预测专门针对第谷超新星激波的情况，在那里有证据表明加速宇宙射线的光谱比传统的扩散激波加速理论所预期的要陡峭。我们表明，如果第谷超新星激波附近的中性氢的分数为~70-90，那么加速质子的光谱陡峭于$p^{-4}$可能是电荷交换反应和相关的中性返回通量的自然结果。对于能量低于~100-1000 GeV的粒子，其扩散长度小于或最多可与激波上游电荷交换和电离的路径长度相当，这种现象会影响光谱形状。
The presence of neutral hydrogen in the shock proximity changes the structure of the shock and affects the spectra of particles accelerated through the first-order Fermi mechanism. This phenomenon has profound implications for the interpretation of the multifrequency spectra of radiation from supernova remnants. Neutrals that undergo charge exchange with hot ions downstream of the shock may result in fast neutrals moving towards the upstream gas, where they can suffer additional charge exchange or ionisation reactions, thereby depositing energy and momentum upstream. Here we discuss the implications of this neutral return flux, which was already predicted in our previous work on neutral mediated supernova shocks, and show how the spectra of accelerated particles turn out to be appreciably steeper than $p^{-4}$, thereby affecting the gamma ray spectra from supernova remnants in general and from Tycho specifically. The theory that describes non-linear diffusive shock acceleration in the presence of neutral hydrogen has been developed in recent years. Here we use a semi-analytical theory developed in previous work and specialise our predictions to the case of the Tycho supernova shock, where there is evidence that the spectrum of the accelerated cosmic rays is steeper than expected from the traditional theory of diffusive shock acceleration. We show that, if the fraction of neutral hydrogen in the vicinity of the Tycho supernova shock is, as suggested by observations, ~70-90, then spectra of accelerated protons steeper than $p^{-4}$ may be a natural consequence of charge exchange reactions and the associated neutral return flux. The spectral shape is affected by this phenomenon for particles with energies below ~100-1000 GeV, for which the diffusion length is less than or at most comparable to the pathlength of charge exchange and ionisation upstream of the shock.
年轻超新星遗迹中的宇宙射线加速
影响因子：
4.8
作者：
Schure K
通讯作者：
Schure K