伽玛暴初始洛仑兹因子和中心引擎的活动时标

发布时间：2018-04-01 23:10

本文选题：伽玛射线暴　切入点：早期光学余辉　出处：《广西大学》2011年硕士论文

【摘要】：本文首先简要介绍近年来伽玛暴的观测和理论进展,特别是Swift和Fermi卫星发射以来所取得的一些重大突破和对伽玛暴新的认识,随后细致阐述我们基于观测数据对伽玛暴火球初始洛仑兹因子和中心引擎活动时间分析的研究结果。伽玛暴火球是极端相对论性的,初始洛伦兹因子是很重要的物理参量。按照火球标准模型,在薄壳层情形下,火球被周围介质减速而在早期余辉中呈现一个显著的光滑鼓包。该鼓包的峰值时间tp可以用以限定火球初始洛伦兹因子。我们细致地研究了具有早期光学和X射线余辉光变中呈现光滑鼓包成份的伽玛暴,计算这些暴火球初始洛仑兹因子Γ0和减速半径Rd,发现Γ0=100—300左右和Rd=2×1017cm左右。我们发现了各向同性能量和初始洛仑兹因子之间存在紧密的关系,r0≈182 E0.25/iso,r,52。这个关系不仅对伽玛暴辐射物理提供强的限制,而且提供了估算长暴的初始洛伦兹因子经验公式。伽玛暴中心引擎活动时标是伽玛暴分类的重要参量。Swift卫星的观测对以暴本身辐射持续时间的分类法提出了严峻挑战,因为Swift卫星观测到暴后显著的x射线耀发。我们以最后一个X射线耀峰值时刻来标定中心引擎的活动时间TCE,发现三分之一伽玛暴在瞬时辐射结束后没有明显的耀发活动,而是呈现幂律衰减,对于这些伽玛暴T90可以很好的表征中心引擎的活动时间TCE,但是三分之二的暴是在暴后有明显的x射线耀发活动。在此类样本中有5个特殊伽玛暴,在BAT到XRT整个过程中都是比较剧烈的脉冲和耀发(例如GRB 050724),没有明显的外激波辐射成分。中心引擎的活动时间TCE从几秒到天的数量级不等,也没有出现所谓的双峰分布。我们的结果表明中心引擎的活动时间TCE可能远远大于强,BATSE时期的T90双峰分布可能是由于仪器的选择效应所造成的。
[Abstract]:This paper first briefly introduces the recent progress in observation and theory of gamma-ray bursts, especially some major breakthroughs made since the launch of Swift and Fermi satellites and a new understanding of gamma bursts. The results of our analysis of initial Lorentz factor and central engine activity time of gamma-ray storm fireball based on observation data are described in detail. The gamma-ray burst fireball is extremely relativistic, and the initial Lorentz factor is an important physical parameter. According to the fireball standard model, in the case of thin shell, The fireball is decelerated by the surrounding medium and presents a significant smooth bulge in the early afterglow. The peak time of the fireball, tp, can be used to limit the initial Lorentz factor of the fireball. We have studied in detail the initial Lorentz factor of the fireball with early optical and X-ray emission. A gamma-ray burst with smooth bulge components in the line afterglow variation, By calculating the initial Lorentz factor 螕 0 and the deceleration radius R d of these fireballs, we find that 螕 0 100 300 and Rd=2 脳 1017cm have a close relation between isotropic energy and initial Lorentz factor. Gamma storm radiation physics provides strong limits, An empirical formula of the initial Lorentz factor for estimating long bursts is also provided. The observation of Swift satellite, which is an important parameter of gamma storm classification, presents a severe challenge to the classification of the radiation duration of the storm itself. Because the Swift satellite observed significant post-burst x-ray flares, we calibrated the activity time of the central engine at the last X-ray peak time, and found that the 1/3 gamma-ray burst had no significant flare activity after the instantaneous radiation ended. But it's power law decay, and for these gamma-ray bursts T90 is a very good representation of the activity time of the central engine, but 2/3 of the bursts are obviously x-ray flares after a storm. There are five special gamma bursts in this sample. During the whole process from BAT to XRT, there are more intense pulses and flares (for example, GRB 050724, no obvious external shock radiation.) the activity time of the center engine is from a few seconds to the order of magnitude of the sky. Our results show that the activity time TCE of the central engine may be much larger than the T90 bimodal distribution during the strong BATSE period, which may be due to the selection effect of the instrument.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：P172.3

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