Monte Carlo simulations of relativistic radiation-mediated shocks: II. photon-starved regime
Monte Carlo simulations of relativistic radiation-mediated shocks: II. photon-starved regime
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相对论辐射介导冲击的蒙特卡罗模拟：II。
DOI：
10.1093/mnras/stz3591
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发表时间：
2019
影响因子：
4.8
通讯作者：
Nagataki Shigehiro
中科院分区：
文献类型：
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作者：
Ito Hirotaka;Levinson Amir;Nagataki Shigehiro
辐射介导的冲击（RMS）在塑造许多瞬态中观察到的早期发射中起着关键作用。在大多数情况下，例如超新星、11GRB和中子星星合并中的激波爆发，上游等离子体没有辐射，最终到达观察者的光子主要在激波内部和下游产生。预测所观察到的光谱需要详细的计算的冲击结构和热力学状态，适当的冲击微观物理。我们给出了光子饥饿RMS的自洽Monte Carlo模拟结果，这些结果产生了从亚相对论性（βsh= 0.1）到高度相对论性（Γsh= 20）的宽范围激波速度的激波结构和发射。我们的模拟证实，在相对论RMS中，直接下游温度由指数对产生调节，范围从50 keV（βsh= 0.5）到200 keV（Γsh= 20）。在较低的速度下，温度变得对激波速度敏感，在βsh= 0.1时，kT <0.5 keV。我们还证实，在相对论冲击的不透明度是完全占主导地位的新创建的对，这对突破物理学具有重要意义。我们发现到对优势的转变大约发生在βsh= 0.5时。在所有的实验中，我们发现低于νFν峰的光谱比普朗克分布要软得多。这对快速和相对论爆发中的光发射及其探测具有重要意义。讨论了GRB 060218和GRB 170817A的应用。
Radiation-mediated shocks (RMS) play a key role in shaping the early emission observed in many transients. In most cases, e.g. shock breakout in supernovae, llGRBs, and neutron star mergers, the upstream plasma is devoid of radiation, and the photons that ultimately reach the observer are generated predominantly inside and downstream of the shock. Predicting the observed spectrum requires detailed calculations of the shock structure and thermodynamic state that account properly for the shock microphysics. We present results of self-consistent Monte Carlo simulations of photon-starved RMS, which yield the shock structure and emission for a broad range of shock velocities, from subrelativistic (βsh= 0.1) to highly relativistic (Γsh= 20). Our simulations confirm that in relativistic RMS the immediate downstream temperature is regulated by exponential pair creation, ranging from 50 keV at βsh= 0.5–200 keV at Γsh= 20. At lower velocities, the temperature becomes sensitive to the shock velocity, withkT∼ 0.5 keV at βsh= 0.1. We also confirm that in relativistic shocks the opacity is completely dominated by newly created pairs, which has important implications for the breakout physics. We find the transition to pair dominance to occur at βsh= 0.5 roughly. In all cases examined, the spectrum below the νFνpeak has been found to be substantially softer than the Planck distribution. This has important implications for the optical emission in fast and relativistic breakouts, and their detection. The applications to GRB 060218 and GRB 170817A are discussed.