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arXiv 0811.1038astro-ph
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伽马射线暴余辉的统一观点

A unifying view of Gamma Ray Burst Afterglows

G. Ghisellini, M. Nardini, G. Ghirlanda, A. Celotti

摘要:

我们选择了33个伽马射线暴(GRB)的样本,雨燕探测到的,与已知的红移和光学消光在主机帧。为此,我们构建了去吸收和K校正的X射线和光学静止框架光变曲线。这些被建模为两个组成部分的总和:发射的前向冲击由于相互作用的火球与环爆介质和一个额外的组件,在一个完全唯象的方式处理。除其他可能性外,后者可以被确定为由长寿命的中央发动机产生的“晚瞬发”排放,其机制类似于负责产生“标准”早瞬发辐射的机制。除了耀斑或再增亮,我们不建模,我们发现一个很好的协议与数据,尽管他们的复杂性和多样性。虽然部分基于一个现象学模型与相对大量的自由参数,我们相信,我们的研究结果是建设一个更物理的情况下迈出的第一步。我们的方法使我们能够通过一个相对简单的方案,以一种连贯的方式解释光学和X射线余辉的行为。在这种背景下,可以解释为什么有时没有观察到喷流中断;为什么即使观察到喷流中断,它通常是彩色的;为什么喷流中断时间后的陡峭度通常比预测的要浅。最后,发现在浅相之后的晚期瞬发发射的衰减斜率与由回退物质的吸积率所预期的时间曲线(即与t^{-5/3}成比例)非常相似,这表明这可能是中央发动机可以长时间活动的原因。

英文摘要:

We selected a sample of 33 Gamma Ray Bursts (GRBs) detected by Swift, with known redshift and optical extinction at the host frame. For these, we constructed the de-absorbed and K-corrected X-ray and optical rest frame light curves. These are modelled as the sum of two components: emission from the forward shock due to the interaction of a fireball with the circum-burst medium and an additional component, treated in a completely phenomenological way. The latter can be identified, among other possibilities, as "late prompt" emission produced by a long lived central engine with mechanisms similar to those responsible for the production of the "standard" early prompt radiation. Apart from flares or re-brightenings, that we do not model, we find a good agreement with the data, despite of their complexity and diversity. Although based in part on a phenomenological model with a relatively large number of free parameters, we believe that our findings are a first step towards the construction of a more physical scenario. Our approach allows us to interpret the behaviour of the optical and X-ray afterglows in a coherent way, by a relatively simple scenario. Within this context it is possible to explain why sometimes no jet break is observed; why, even if a jet break is observed, it is often chromatic; why the steepening after the jet break time is often shallower than predicted. Finally, the decay slope of the late prompt emission after the shallow phase is found to be remarkably similar to the time profile expected by the accretion rate of fall-back material (i.e. proportional to t^{-5/3}), suggesting that this can be the reason why the central engine can be active for a long time.

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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