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arXiv 1306.1699astro-ph.HEastro-ph.CO
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超长型GRB 111209 A- II。余辉和余辉性质的提示

The ultra-long GRB 111209A - II. Prompt to afterglow and afterglow properties

G. Stratta, B. Gendre, J. L. Atteia, M. Boër, D. M. Coward, M. De Pasquale, E. Howell, A. Klotz, S. Oates, L. Piro

摘要:

红移z=0.677的“超长”伽马射线暴GRB 111209 A是迄今为止观测到的最长的GRB,其静止帧瞬发持续时间约为4小时。为了解释爆发的异常长寿,一个低金属丰度的蓝超巨星祖先已经被调用。在这项工作中,我们进一步调查这一奇特的爆发进行多波段的时间和光谱分析的提示和余辉发射。我们使用来自Swift,Konus Wind,XMM-Newton,TAROT以及其他地面光学和射电望远镜的专有和公开数据。我们发现了一些可能与这次爆发的特殊性质有关的特殊性质,即:i)在第一次Swift/BAT触发后约2ks,在γ射线中观察到的显著耀斑的峰值时期之间测量到前所未有的410+/-50s的大光学延迟; ii)如果在瞬发发射期间的光学和X射线/伽马射线光子共享共同的起源,如它们类似的时间行为所表明的,则环暴环境中应引入一定量的尘埃,与休息帧视觉尘埃消光AV=0.3-1.5马格; iii)在结束的X射线“陡峭的衰减阶段”和X射线余辉开始之前,我们检测到一个硬光谱额外的幂律成分的存在从来没有透露至今。相反,自瞬发结束以来的光学余辉显示出更常见的性质,具有指数α =1.6+/-0.1的通量幂律衰减和1.1天的后期再增亮特征。我们讨论了我们的研究结果的背景下,到目前为止,复杂的多波段伽玛射线暴现象的几种可能的解释。我们还试图利用我们的研究结果,以进一步限制这种异常长的伽玛暴的祖性质,建议一个二元通道形成的建议蓝超巨星祖。

英文摘要:

The "ultra-long" Gamma Ray Burst GRB 111209A at redshift z=0.677, is so far the longest GRB ever observed, with rest frame prompt emission duration of ~4 hours. In order to explain the bursts exceptional longevity, a low metallicity blue supergiant progenitor has been invoked. In this work, we further investigate this peculiar burst by performing a multi-band temporal and spectral analysis of both the prompt and the afterglow emission. We use proprietary and publicly available data from Swift, Konus Wind, XMM-Newton, TAROT as well as from other ground based optical and radio telescopes. We find some peculiar properties that are possibly connected to the exceptional nature of this burst, namely: i) an unprecedented large optical delay of 410+/-50 s is measured between the peak epochs of a marked flare observed also in gamma-rays after about 2 ks from the first Swift/BAT trigger; ii) if the optical and X-ray/gamma-ray photons during the prompt emission share a common origin, as suggested by their similar temporal behavior, a certain amount of dust in the circumburst environment should be introduced, with rest frame visual dust extinction of AV=0.3-1.5 mag; iii) at the end of the X-ray "steep decay phase" and before the start of the X-ray afterglow, we detect the presence of a hard spectral extra power law component never revealed so far. On the contrary, the optical afterglow since the end of the prompt emission shows more common properties, with a flux power law decay with index alpha=1.6+/-0.1 and a late re-brightening feature at 1.1 day. We discuss our findings in the context of several possible interpretations given so far to the complex multi-band GRB phenomenology. We also attempt to exploit our results to further constrain the progenitor nature properties of this exceptionally long GRB, suggesting a binary channel formation for the proposed blue supergiant progenitor.

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