External Shock in a Multi-bursting Gamma-Ray Burst: Energy Injection Phase Induced by the Later Launched Ejecta
External Shock in a Multi-bursting Gamma-Ray Burst: Energy Injection Phase Induced by the Later Launched Ejecta
复制标题
多爆发伽马射线爆发中的外部冲击：后来发射的喷射物引起的能量注入阶段
DOI：
10.3847/1538-4357/aa9f15
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发表时间：
2018
影响因子：
4.9
通讯作者：
Liang En-Wei
中科院分区：
文献类型：
--
作者：
Lin Da-Bin;Huang Bao-Quan;Liu Tong;Gu Wei-Min;Mu Hui-Jun;Liang En-Wei
伽玛射线暴（GRB）的中心引擎可能是间歇性的，并发射几个事件的喷出物分开了一个很长的静止间隔。在这种情况下，由于第一次发射的喷出物传播到环爆介质中而形成外部冲击，并且稍后发射的喷出物可能在稍后的时期与外部冲击相互作用。由于内部耗散，可以在较晚的时间（tjet）观察到较晚发射的喷出物。本文研究了tb与tjet的关系，tb是后来发射的喷出物与形成的外激波碰撞的时间。结果表明，tb与tjet的关系取决于后一次发射的喷出物的体洛仑兹因子（Γjet）和环爆介质的密度（ρ）。如果Γjet或ρ的值较低，则tb将显著大于tjet。然而，如果Γjet或ρ的值非常大，则可以找到tb tjet。我们的结果可以解释伽玛暴中光辐射相对于γ射线/X射线辐射的大滞后，GRB 111209A。对于有前兆的伽玛暴，我们的结果表明，在主瞬发发射阶段可能会出现能量注入外部冲击，从而出现多个外部反向冲击。根据我们的模型，我们估计了GRB 160625 B的第二次发射的喷出物的洛伦兹因子。
Central engines of gamma-ray bursts (GRBs) may be intermittent and launch several episodes of ejecta separated by a long quiescent interval. In this scenario, an external shock is formed due to the propagation of the first launched ejecta into the circum-burst medium and the later launched ejecta may interact with the external shock at a later period. Owing to the internal dissipation, the later launched ejecta may be observed at a later time (tjet). In this paper, we study the relation of tb and tjet, where tb is the collision time of the later launched ejecta with the formed external shock. It is found that the relation of tb and tjet depends on the bulk Lorentz factor (Γjet) of the later launched ejecta and the density (ρ) of the circum-burst medium. If the value of Γjet or ρ is low, the tb would be significantly larger than tjet. However, the tb ∼ tjet can be found if the value of Γjet or ρ is significantly large. Our results can explain the large lag of the optical emission relative to the γ-ray/X-ray emission in GRBs, e.g., GRB 111209A. For GRBs with a precursor, our results suggest that the energy injection into the external shock and thus more than one external-reverse shock may appear in the main prompt emission phase. According to our model, we estimate the Lorentz factor of the second launched ejecta in GRB 160625B.