脉冲星风星云（II）的混响：“薄壳”演化的剖析
Reverberation of pulsar wind nebulae (II): Anatomy of the "thin-shell'' evolution
摘要：
在其早期演化过程中，脉冲星风星云（PWN）扫过超新星喷出物的内部，形成一个薄而大的壳层。后来，当超新星遗迹的反向冲击到达壳层时，演化变得更加复杂，在大多数情况下，膨胀恢复为压缩：这个后期阶段称为“混响”。到目前为止，为理解这一阶段所做的计算大多是在薄壳近似下进行的，其中PWN半径的演化被同化为在PWN的内部压力和超新星遗迹的外部压力的影响下的扫掠壳。尽管薄壳方法似乎相当合理，但其实现迄今为止并不准确，其正确性从未经过测试。外部压力被天真地假设为在整个演化过程中根据Sedov解（或其常数部分）进行缩放。薄壳假设本身在过程中失败了，因为与PWN的尺寸相比，壳不再薄。在这里，通过结合数值模型，尺寸参数和解析近似，我们提出了一个详细的分析的PWN与超新星遗迹的相互作用。我们提供了一个新的解析近似的外部压力，超越了Sedov解决方案，和一个修订后的“薄壳”能够再现数值模拟的结果。最后，我们计算的效率，PWN在混响期间被压缩在一个广泛的人口来源。
英文摘要：
During its early evolution, a pulsar wind nebula (PWN) sweeps the inner part of the supernova ejecta and forms a thin massive shell. Later on, when the shell has been reached by the reverse shock of the supernova remnant, the evolution becomes more complex, in most cases reverting the expansion into a compression: this later phase is called "reverberation". Computations done so far to understand this phase have been mostly performed in the thin-shell approximation, where the evolution of the PWN radius is assimilated to that of the swept-up shell under the effect of both the inner pressure from the PWN, and the outer pressure from the supernova remnant. Despite the thin-shell approach seems rather justifiable, its implementations have so far been inaccurate, and its correctness, never tested. The outer pressure was naively assumed to be scaled according to the Sedov solution (or a constant fraction of it) along the entire evolution. The thin-shell assumption itself fails along the process, being the shell no longer thin in comparison with the size of the PWN. Here, through a combination of numerical models, dimensional arguments, and analytic approximations, we present a detailed analysis of the interaction of the PWN with the supernova remnant. We provide a new analytic approximation of the outer pressure, beyond the Sedov solution, and a revised "thin-shell" able to reproduce results from numerical simulations. Finally, we compute the efficiency by which the PWN is compressed during reverberation over a wide population of sources.
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