第谷超新星遗迹中Balmer主导激波的cosmic-ray前兆模型
A cosmic-ray precursor model for a Balmer-dominated shock in Tycho's supernova remnant
摘要：
我们提出了一个依赖于时间的宇宙射线修正激波模型，计算的H-α发射率分布与Lee等人（2007）在Tycho超新星遗迹中g节点处Balmer主导激波之前的H-α通量增加非常一致。宇宙线分量对热分量的反反应在双流体近似下处理，并且我们包括热粒子注入和由于前体中的声学不稳定性引起的能量转移。我们的模型的瞬态，描述了当前状态的冲击在节点g，发生在从热气体为主的冲击到光滑的宇宙射线为主的冲击的演变过程中。假设到第谷遗迹的距离为2.3 kpc，我们得到的宇宙射线扩散系数、注入参数和能量传递的时间尺度分别为10^{24} cm^{2} s^{-1}、4.2x10^{-3}和426 y。我们还研究了快速（300 km s^{-1} - 3000 km s^{-1}）、时间渐近稳定激波的参数空间，并确定了一个解的分支，在这个分支中，宇宙线前兆的温度通常达到2- 6 × 10 ^{4} K，而通过前兆的气流的整体加速度小于10 km s^{-1}。这些解决方案属于低宇宙射线加速效率的制度，是相对不敏感的冲击参数。这种低宇宙射线加速效率的解决方案分支可以提供一个自然的解释，在许多超新星遗迹的非辐射冲击中观察到的H-α窄分量的线加宽。
英文摘要：
We present a time-dependent cosmic-ray modified shock model for which the calculated H-alpha emissivity profile agrees well with the H-alpha flux increase ahead of the Balmer-dominated shock at knot g in Tycho's supernova remnant, observed by Lee et al (2007). The backreaction of the cosmic ray component on the thermal component is treated in the two-fluid approximation, and we include thermal particle injection and energy transfer due to the acoustic instability in the precursor. The transient state of our model that describes the current state of the shock at knot g, occurs during the evolution from a thermal gas dominated shock to a smooth cosmic-ray dominated shock. Assuming a distance of 2.3 kpc to Tycho's remnant we obtain values for the cosmic ray diffusion coefficient, the injection parameter, and the time scale for the energy transfer of 10^{24} cm^{2} s^{-1}, 4.2x10^{-3}, and 426 y, respectively. We have also studied the parameter space for fast (300 km s^{-1} - 3000 km s^{-1}), time-asymptotically steady shocks and have identified a branch of solutions, for which the temperature in the cosmic ray precursor typically reaches 2-6x10^{4} K and the bulk acceleration of the flow through the precursor is less than 10 km s^{-1}. These solutions fall into the low cosmic ray acceleration efficiency regime and are relatively insensitive to shock parameters. This low cosmic ray acceleration efficiency branch of solutions may provide a natural explanation for the line broadening of the H-alpha narrow component observed in non-radiative shocks in many supernova remnants.
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