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arXiv 2105.09323astro-ph.HE
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短伽马射线暴瞬发辐射的全球数值模式

A global numerical model of the prompt emission in short gamma-ray bursts

Hirotaka Ito, Oliver Just, Yuki Takei, Shigehiro Nagataki

摘要:

我们提出了第一个全球性的模型,从一个短的伽马射线暴,一致地描述了中央黑洞(BH)环面系统的演变,通过多组分合并喷出物,过渡到自由膨胀的射流的传播,和光球发射的相对论性喷流。为此,我们进行了一个特殊的相对论中微子流体动力学模拟的粘性BH-环面系统,这是合并后约500毫秒形成的,并包围动态喷出物,以及中子星风,随着喷流,注入附近的中央BH。在后处理步骤中,我们使用相对论蒙特卡罗辐射转移代码计算光球发射。结果发现,风从环面留下了强烈的印记,以及对射流的排放造成狭窄的准直和快速的时间变化。发射的视角依赖性引起光谱峰值能量E_p、各向同性能量E_iso和峰值亮度L_p之间的相关性,这可以为Amati关系和Yonetoku关系提供自然的解释。我们还发现,对于来自喷流核心的发射,偏振度很小(<2%),而它往往随着核心外部的视角而增加,并且对于大于峰值能量的能量,偏振度可以高达~10-40%。最后,我们的模型与GRB 170817 A的比较强烈反对光球发射的情况下,因此支持替代方案,如茧冲击爆发。

英文摘要:

We present the first global model of prompt emission from a short gamma-ray burst that consistently describes the evolution of the central black-hole (BH) torus system, the propagation of the jet through multi-component merger ejecta, the transition into free expansion, and the photospheric emission from the relativistic jet. To this end, we perform a special relativistic neutrino-hydrodynamics simulation of a viscous BH-torus system, which is formed about 500ms after the merger and is surrounded by dynamical ejecta as well as neutron star winds, along with a jet that is injected in the vicinity of the central BH. In a post-processing step, we compute the photospheric emission using a relativistic Monte-Carlo radiative transfer code. It is found that the wind from the torus leaves a strong imprint on the jet as well as on the emission causing narrow collimation and rapid time variability. The viewing angle dependence of the emission gives rise to correlations among the spectral peak energy, E_p, isotropic energy, E_iso, and peak luminosity, L_p, which may provide natural explanations for the Amati- and Yonetoku-relations. We also find that the degree of polarization is small for the emission from the jet core (<2%), while it tends to increase with viewing angle outside of the core and can become as high as ~10-40% for energies larger than the peak energy. Finally, the comparison of our model with GRB170817A strongly disfavors the photospheric emission scenario and therefore supports alternative scenarios, such as the cocoon shock breakout.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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