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arXiv 1402.7022astro-ph.HE
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伽马射线暴瞬发

Gamma-Ray Burst Prompt Emission

Bing Zhang

摘要:

伽马射线暴(GRB)瞬发辐射的起源,持续时间从不到一秒到数千秒,经过40多年的观测,仍然没有完全弄清楚。这些不确定性存在于伽玛暴物理学中的几个悬而未决的问题中,包括喷流成分、能量耗散机制、粒子加速机制和辐射机制。最近费米对瞬发辐射的宽带观测加剧了这些领域的争论,激发了激烈的理论研究,引发了非常不同的想法。我将回顾这些争论,并认为,目前的数据表明以下图片:一个准热光谱成分起源于光球的相对论喷出物已被发现在一些伽玛射线暴。即使在某些情况下(例如GRB 090902 B),该分量占主导地位的频谱,在大多数GRB中,该分量要么形成一个次主导的“肩”谱分量在更主要的“带”分量的低能量谱区,或根本无法检测到。主要的“带”光谱分量可能源自由于同步辐射而产生的光学薄区域。伽玛射线暴中心引擎的不同磁化强度可能是观测到的不同的瞬发性质的起源。

英文摘要:

The origin of gamma-ray burst (GRB) prompt emission, bursts of gamma-rays lasting from shorter than one second to thousands of seconds, remains not fully understood after more than 40 years of observations. The uncertainties lie in several open questions in the GRB physics, including jet composition, energy dissipation mechanism, particle acceleration mechanism, and radiation mechanism. Recent broad-band observations of prompt emission with Fermi sharpen the debates in these areas, which stimulated intense theoretical investigations invoking very different ideas. I will review these debates, and argue that the current data suggest the following picture: A quasi-thermal spectral component originating from the photosphere of the relativistic ejecta has been detected in some GRBs. Even though in some cases (e.g. GRB 090902B) this component dominates the spectrum, in most GRBs, this component either forms a sub-dominant "shoulder" spectral component in the low energy spectral regime of the more dominant "Band" component, or is not detectable at all. The main "Band" spectral component likely originates from the optically thin region due to synchrotron radiation. The diverse magnetization in the GRB central engine is likely the origin of the observed diverse prompt emission properties among bursts.

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