[论文解读] Bright X-ray flares in XRF 050406 and GRB 050502B provide evidence for extended central engine activity

D. N. Burrows, P. Romano+32 more|arXiv (Cornell University)|Jun 7, 2005

Gamma-ray bursts and supernovae被引用 1

一句话总结

本文基于XRF 050406和GRB 050502B中明亮X射线耀发的证据，表明长伽马射线暴的中心引擎在瞬时伽马射线辐射结束后仍持续活动数百秒，表明内部激波活动持续时间更长。这些耀发在爆发后数分钟被探测到，挑战了关于中心引擎活动终止的先前假设，并表明能量持续注入火球。

ABSTRACT

Gamma-ray bursts (GRBs) are the most powerful explosions since the Big Bang, with typical energies around 10**51 ergs. Long GRBs (duration > 2 s) are thought to signal the creation of black holes, most likely by collapse of massive stars. The detected signals from the resulting highly relativistic fireball consist of prompt gamma-ray emission (from internal shocks in the fireball) lasting for several seconds to minutes, followed by afterglow emission (from external shocks as the fireball encounters surrounding material) covering a broad range of frequencies from radio through X-rays. Because of the time needed to determine the GRB position, most afterglow measurements have been made hours after the burst, and little is known about the characteristics of afterglows in the minutes following a burst, when the afterglow emission is actively responding to inhomogeneities in both the fireball and the circumburst environment. Here we report our discovery of two bright X-ray flares peaking a few minutes after the burst. These amazingly strong, rapid X-ray flares imply that the central engines of the bursts are active at much later times than previously thought, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.

研究动机与目标

• 研究长伽马射线暴爆发后关键分钟内的余晖辐射特性，这一时期此前观测不足。
• 确定中心引擎活动是否在瞬时伽马射线辐射结束后仍持续存在。
• 探究在爆发后数分钟内探测到的意外明亮X射线耀发的起源。
• 评估晚发X射线耀发对火球模型动力学及能量注入机制的影响。

提出的方法

• 分析Swift/XRT对XRF 050406和GRB 050502B的X射线光 light curves。
• 识别在初始爆发后数分钟内出现的明亮、快速的X射线耀发。
• 将耀发特征与内激波模型进行比较，推断持续的能量注入。
• 利用时间与光谱分析，约束中心引擎活动的持续时间与能量输出。
• 评估耀发特性与非均匀环境中持续火球活动的一致性。

实验结果

研究问题

• RQ1 长伽马射线暴的中心引擎是否在瞬时伽马射线辐射结束后仍保持活动？
• RQ2 在初始爆发后数分钟内探测到的明亮X射线耀发由何原因引起？
• RQ3 晚发耀发如何约束火球的动力学及其与周围物质的相互作用？
• RQ4 观测到的耀发能否由持续能量注入引起的内激波解释？

主要发现

• 在XRF 050406和GRB 050502B中探测到两次明亮的X射线耀发，其峰值出现在初始爆发后约200–300秒。
• 耀发异常强烈且迅速，表明在较晚时刻有显著的能量释放。
• 这些耀发的存在表明，内部激波在瞬时伽马射线辐射结束后仍持续活动数百秒。
• 这些爆发的中心引擎持续活动的时间远超以往认知，挑战了标准火球模型。
• 耀发表明能量持续注入火球，可能源于寿命较长的中心引擎。