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arXiv 0812.1038astro-ph
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伽马射线暴余辉:理论与观测

Gamma-Ray Burst afterglows: theory and observations

A. Panaitescu

摘要:

我讨论了一些理论预期的同步辐射从相对论性的冲击波与周围介质相互作用,作为一个模型的伽玛射线暴余辉,并将它们与观察。余辉通量随时间按幂律演化,爆发期间/之后的明亮闪光,以及由于紧密的喷出物准直而导致的光变曲线断裂是观测证实的主要预测,但应该认识到光变曲线衰减指数与光谱斜率无关(正如预期的那样),光学闪光是相当罕见的,在斯威夫特X射线余辉中更难找到喷射中断。早期的光通量衰减率的放缓是伴随着光谱的演变,表明从喷出物(通电的反向冲击)的排放是占主导地位的光学从正向冲击(通电的环境介质)只有1千秒。然而,需要一个长寿命的反向冲击来解释在许多余辉中观察到的~10天后的缓慢的无线电通量衰减。X射线光变曲线的平台可能是由于爆炸波的平均能量/固体角的变化,证实了伽玛射线暴外流的另外两个预期特征:能量注入和角结构。后者也更可能是一些光学光变曲线中快速上升的起源。为了解释彩色和消色差余辉光变曲线突变的存在,整个图像必须更加复杂,并包括一个新的机制,偶尔占主导地位的爆炸波的排放:无论是后期内部冲击波或散射(散装和/或逆康普顿)的爆炸波排放的外流内部。

英文摘要:

I discuss some theoretical expectations for the synchrotron emission from a relativistic blast-wave interacting with the ambient medium, as a model for GRB afterglows, and compare them with observations. An afterglow flux evolving as a power-law in time, a bright optical flash during/after the burst, and a light-curve break due to a tight ejecta collimation are the major predictions that were confirmed observationally, but it should be recognized that light-curve decay indices are not correlated with the spectral slopes (as would be expected), optical flashes are quite rare, and jet-breaks harder to find in Swift X-ray afterglows. The slowing of the early optical flux decay rate is accompanied by a spectral evolution, indicating that the emission from ejecta (energized by the reverse shock) is dominant in the optical over that from the forward shock (which energizes the ambient medium) only up to 1 ks. However, a long-lived reverse shock is required to account for the slow radio flux decays observed in many afterglows after ~10 day. X-ray light-curve plateaus could be due to variations in the average energy-per-solid-angle of the blast-wave, confirming to two other anticipated features of GRB outflows: energy injection and angular structure. The latter is also the more likely origin of the fast-rises seen in some optical light-curves. To account for the existence of both chromatic and achromatic afterglow light-curve breaks, the overall picture must be even more complex and include a new mechanism that dominates occasionally the emission from the blast-wave: either late internal shocks or scattering (bulk and/or inverse-Compton) of the blast-wave emission by an outflow interior to it.

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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