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arXiv 2011.02973astro-ph.HE
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伽马射线暴瞬发相的后向散射主导瞬发模型

A backscattering dominated prompt emission model for the prompt phase of Gamma ray bursts

Mukesh K Vyas, Asaf Pe'er, David Eichler

摘要:

当伽马射线暴(GRB)喷流穿过坍缩的恒星时,它会在前面捕获一个重子软木塞。在这里,我们探索了一个GRB的瞬发发射模型,在这个模型中,喷流不会穿过软木塞,而是在流的深处发射的光子,主要是通过对湮灭,在膨胀的软木塞内部散射,当它们从后面推动软木塞时,大部分光子从软木塞的后端逃逸。由于软木塞的相对论运动,这些光子很容易被靠近射流轴的观察者看到,峰值在$\varepsilon_{peak}\sim~few \times 100 keV$。我们发现,这个模型自然地解释了几个关键的观测特征,包括:(1)高能量幂律指数$β_1 \sim -2 {~\rm to~} -5$与中间的热光谱区域;(2)即时发射光变曲线的衰减$\sim t^{-2}$ ;(3)软光子的延迟;(4)峰值能量-各向同性能量(所谓的Amati)相关,$\varepsilon_{peak} \sim \varepsilon_{iso}^m$,与$m\sim 0.45$,从不同的视角产生。在低光度下,我们的模型预测了一个可观察到的关闭阿马蒂关系。(4)光谱半峰全宽(FWHM)和时间之间的反相关性为$t^{-1}$。(5)时间演化$\varepsilon_{peak} \sim t^{-1}$,伴随着高能量谱斜率随时间的增加。(6)观测到的伽玛暴粒子数中峰值能量$\varepsilon_{peak}$的分布。该模型适用于单脉冲伽玛暴的光变曲线和相应的光谱。我们讨论了我们的模型的后果,鉴于当前和未来的即时排放观测。

英文摘要:

As gamma-ray burst (GRB) jet drills its way through the collapsing star, it traps a baryonic cork ahead of it. Here we explore a prompt emission model for GRBs in which the jet does not cross the cork, but rather photons that are emitted deep in the flow largely by pair annihilation are scattered inside the expanding cork and escape largely from the back end of it as they push it from behind. Due to the relativistic motion of the cork, these photons are easily seen by an observer close to the jet axis peaking at $\varepsilon_{peak}\sim~few \times 100 keV$. We show that this model naturally explains several key observational features including: (1) High energy power law index $β_1 \sim -2 {~\rm to~} -5$ with an intermediate thermal spectral region; (2) decay of the prompt emission light curve as $\sim t^{-2}$; (3) Delay of soft photons; (4) peak energy - isotropic energy (the so-called Amati) correlation, $\varepsilon_{peak} \sim \varepsilon_{iso}^m$, with $m\sim 0.45$, resulting from different viewing angles. At low luminosities, our model predicts an observable turn off in the Amati relation. (4) An anti-correlation between the spectral full width half maxima (FWHM) and time as $t^{-1}$. (5) Temporal evolution $\varepsilon_{peak} \sim t^{-1}$, accompanied by an increase of the high energy spectral slope with time. (6) Distribution of peak energies $\varepsilon_{peak}$ in the observed GRB population. The model is applicable for a single pulse GRB lightcurves and respective spectra. We discuss the consequence of our model in view of the current and future prompt emission observations.

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