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arXiv 0812.4677astro-ph
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伽玛暴瞬发和高纬辐射的现实解析模型

Realistic analytic model for the prompt and high latitude emission in GRBs

F. Genet, J. Granot

摘要:

雨燕卫星观测到的大多数伽马射线暴(GRB)在其X射线光变曲线中显示出早期快速衰变相(RDP),这通常是瞬发伽玛射线发射的平滑延续,强烈暗示这是它的尾部。然而,其背后的机制尚不清楚。这种RDP最受欢迎的型号是高纬度发射(HLE)。虽然HLE在许多模型中是预期的即时伽玛射线暴的排放,如流行的内部冲击模型,也有一些模型,它是不预期的,如零星的磁重联事件。因此,检验RDP与HLE是否一致有助于区分不同的瞬发排放模型。我们解决这个问题,通过建模的即时发射的总和,其单独的脉冲与他们的HLE尾巴。对于幂律和带函数发射谱,得到了观测通量密度的解析表达式。对于内部冲击,观测到的瞬时频谱非常接近于发射的频谱,并且在RDP期间也应该由带函数很好地描述。我们的模型自然地产生,观测到的光谱软化和陡峭的通量衰减。RDP期间观测到的通量最初由最后一个脉冲的尾部主导,但是一个或多个较早脉冲的尾部可以在以后变得主导。此外,将多个重叠脉冲建模为单个较宽脉冲将过度预测发射尾部。因此,在检验HLE的预测时,我们应该非常小心,并对瞬发GRB发射和RDP进行时间和光谱的组合拟合。

英文摘要:

Most gamma-ray bursts (GRBs) observed by the Swift satellite show an early rapid decay phase (RDP) in their X-ray lightcurve, which is usually a smooth continuation of the prompt gamma-ray emission, strongly suggesting that it is its tail. However, the mechanism behind it is still not clear. The most popular model for this RDP is High Latitude Emission (HLE). While HLE is expected in many models for the prompt GRB emission, such as the popular internal shocks model, there are models in which it is not expected, such as sporadic magnetic reconnection events. Therefore, testing whether the RDP is consistent with HLE can help distinguish between different prompt emission models. We address this question by modeling the prompt emission as the sum of its individual pulses with their HLE tails. Analytic expressions for the observed flux density are obtained for power-law and Band function emission spectra. For internal shocks the observed instantaneous spectrum is very close to the emitted one, and should be well described by a Band function also during the RDP. Our model naturally produces, the observed spectral softening and steepening of the flux decay. The observed flux during the RDP is initially dominated by the tail of the last pulse, but the tails of one or more earlier pulses can become dominant later on. Moreover, modeling several overlapping pulses as a single wider pulse would over-predict the emission tail. Thus, one should be very careful when testing the predictions of HLE and do a combined temporal and spectral fit of the prompt GRB emission and the RDP.

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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