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arXiv 1206.6770astro-ph.HEastro-ph.CO
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在瞬时GRB发射模型中解释XRT早期急剧衰减

Accounting for the XRT early steep decay in models of the prompt GRB emission

R. Hascoët, F. Daigne, R. Mochkovitch

摘要:

对伽玛暴早期X射线余辉的Swift-XRT观测表明,它通常开始于一个陡峭的衰变相。这种早期急剧衰减的一个可能的起源是高纬度的发射,当相对论外流中最后一个耗散区的轴上发射被关闭时,这种发射仍然存在。我们希望确定各种瞬时发射模型中的哪一个与这种解释相一致。我们依次考虑内部冲击,光球发射,和磁重联,并获得在每种情况下的提示阶段结束时的典型衰减时标。只有内部的冲击自然预测衰变的时间尺度相当于爆发的持续时间,需要解释XRT观测高纬度的排放。在光球模型中,高纬度辐射的衰变时间尺度太短,因此观测到的衰变必须与中心引擎的有效和一般行为相对应。重新连接模型需要一些特别的假设来与数据相一致,当重新连接过程的更好描述变得可用时,这些假设必须得到验证。

英文摘要:

The Swift-XRT observations of the early X-ray afterglow of GRBs show that it usually begins with a steep decay phase. A possible origin of this early steep decay is the high latitude emission that subsists when the on-axis emission of the last dissipating regions in the relativistic outflow has been switched-off. We wish to establish which of various models of the prompt emission are compatible with this interpretation. We successively consider internal shocks, photospheric emission, and magnetic reconnection and obtain the typical decay timescale at the end of the prompt phase in each case. Only internal shocks naturally predict a decay timescale comparable to the burst duration, as required to explain XRT observations in terms of high latitude emission. The decay timescale of the high latitude emission is much too short in photospheric models and the observed decay must then correspond to an effective and generic behavior of the central engine. Reconnection models require some ad hoc assumptions to agree with the data, which will have to be validated when a better description of the reconnection process becomes available.

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