A Global Numerical Model of the Prompt Emission in Short Gamma-ray Bursts
A Global Numerical Model of the Prompt Emission in Short Gamma-ray Bursts
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DOI：
10.3847/1538-4357/ac0cf9
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
Hirotaka Ito;O. Just;Y. Takei;S. Nagataki
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作者：
Hirotaka Ito;O. Just;Y. Takei;S. Nagataki
我们提出了第一个全球性的短伽玛射线暴（GRB），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，光球发射的相对论射流的即时发射模型。为此，我们进行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，并包围着动态喷出物以及中子星星风，沿着与喷射，是在中央BH附近注入。在后处理步骤中，我们使用相对论蒙特卡罗辐射传输代码计算光球发射。结果发现，风从环面留下了强烈的印记，以及对喷流的排放，造成狭窄的准直和快速的时间变化。发射对视角的依赖性引起光谱峰值能量Ep、各向同性能量Eiso和峰值亮度Lp之间的相关性，这可以为Amati和Yonetoku关系提供自然的解释。我们还发现，偏振度是小的发射从喷流的核心（102%），而它往往增加与观察角度以外的核心，并可以成为高达100%-40%的能量大于峰值能量。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。
We present the first global model of prompt emission from a short gamma-ray burst (GRB) that consistently describes the evolution of the central black hole (BH) torus system, the propagation of the jet through multicomponent 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 500 ms 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 postprocessing 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 dependence of the emission on viewing angle 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 emission from the jet core (≲2%), while it tends to increase with viewing angle outside the core and can become as high as ∼10%–40% for energies larger than the peak energy. Finally, the comparison of our model with GRB 170817A strongly disfavors the photospheric emission scenario and therefore supports alternative scenarios, such as cocoon shock breakout.