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arXiv 1901.01775astro-ph.HE
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关于伽马射线暴中的$α$ -强度相关:具有变熵的次光球加热

On the $α$-Intensity Correlation in Gamma-Ray Bursts: Subphotospheric Heating with Varying Entropy

Felix Ryde, Hoi-Fung Yu, Hüsne Dereli-Bégué, Christoffer Lundman, Asaf Pe'er, Liang Li

摘要:

伽马射线暴(GRB)瞬发相的辐射机制可以通过光谱性质之间的相关性来研究。在这里,我们重新审视相关的瞬时流量,$F$,和光子指数低于光谱中断,$α$,在个别的发射脉冲,通过研究费米/GBM伽玛暴目录中的38个最突出的脉冲。首先,我们搜索签名的偏见,在确定$α$由于有限的光谱覆盖范围(窗口效应)预期在同步加速器的情况下。缺乏这样的特征信号反对最简单的同步加速器模型。相反,我们发现$F$和$α$之间观察到的相关性通常可以用关系$F(t) \propto {\rm e}^{k\,α(t)}$来描述,其中中值$k = 3$。我们认为,这种相关性是一种表现的亚光球加热流与熵的变化。在光变曲线的峰值附近,一个大的熵使光球接近饱和半径,导致一个窄光谱的强发射。随着熵的减小,光球层脱离饱和半径,预计会有较弱的发射和较宽的光谱。这个简单的场景自然会导致强度和光谱形状的相关变化,覆盖了观测范围。

英文摘要:

The emission mechanism during the prompt phase in gamma-ray bursts (GRBs) can be investigated through correlations between spectral properties. Here, we revisit the correlation relating the instantaneous flux, $F$, and the photon index below the spectral break, $α$, in individual emission pulses, by studying the 38 most prominent pulses in the Fermi/GBM GRB catalogue. First, we search for signatures of the bias in the determination of $α$ due to the limited spectral coverage (window effect) expected in the synchrotron case. The absence of such a characteristic signature argues against the simplest synchrotron models. We instead find that the observed correlation between $F$ and $α$ can, in general, be described by the relation $F(t) \propto {\rm e}^{k\,α(t)}$, for which the median $k = 3$. We suggest that this correlation is a manifestation of subphotospheric heating in a flow with a varying entropy. Around the peak of the light curve, a large entropy causes the photosphere to approach the saturation radius, leading to an intense emission with a narrow spectrum. As the entropy decreases the photosphere secedes from the saturation radius, and weaker emission with a broader spectrum is expected. This simple scenario naturally leads to a correlated variation of the intensity and spectral shape, covering the observed range.

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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