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arXiv 1609.04686astro-ph.HE
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关于某些伽马射线暴的射电余辉的缺乏--对它们祖先的了解?

On the Lack of a Radio Afterglow from Some Gamma-ray Bursts - Insight into Their Progenitors?

Nicole M. Lloyd-Ronning, Christopher L. Fryer

摘要:

我们研究了一个明亮的(E_iso > 10^52 erg)伽马射线暴样本的内禀性质,比较了有和没有射电余辉的情况。我们发现,没有射电余辉的爆发样本具有显着较短的瞬发γ射线辐射的平均固有持续时间,并且该持续时间的分布与具有射电余辉的爆发显著不同。虽然没有无线电余辉的样品平均具有较低的各向同性能量,但无线电余辉的缺乏似乎不是简单的能量学的结果,而是可能与环暴密度分布有关的单独物理现象的反映。我们还发现,在没有射电余辉的样品中,各向同性伽马射线能量和固有持续时间之间存在弱相关性,而在观测到射电余辉的样品中则没有。我们给出了可能的解释,为什么可能存在一个样本的伽玛暴没有无线电余辉取决于无线电发射是否来自前向或反向冲击,以及为什么这些突发似乎有本质上较短的即时发射持续时间。我们讨论了我们的研究结果可能对GRB的祖先模型产生的影响。

英文摘要:

We investigate the intrinsic properties of a sample of bright (E_iso > 10^52 erg) gamma-ray bursts, comparing those with and without radio afterglows. We find that the sample of bursts with no radio afterglows has a significantly shorter mean intrinsic duration of the prompt gamma-ray radiation, and the distribution of this duration is significantly different from those bursts with a radio afterglow. Although the sample with no radio afterglow has on average lower isotropic energy, the lack of radio afterglow does not appear to be a result of simply energetics of the burst, but a reflection of a separate physical phenomenon likely related to the circumburst density profile. We also find a weak correlation between the isotropic gamma-ray energy and intrinsic duration in the sample with no radio afterglow, but not in the sample which have observed radio afterglows. We give possible explanations for why there may exist a sample of GRBs with no radio afterglow depending on whether the radio emission comes from the forward or reverse shock, and why these bursts appear to have intrinsically shorter prompt emission durations. We discuss how our results may have implications for progenitor models of GRBs.

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