伽玛射线暴的观测和理论以及双成分喷流的磁驱动模型

发布时间：2018-01-30 13:11

本文关键词： 伽玛射线暴火球激波模型双结构喷流黑洞磁场 BZ机制 BP机制　出处：《华中科技大学》2011年硕士论文　论文类型：学位论文

【摘要】：伽玛射线暴（Gamma-ray Bursts, GRBs，简称伽玛暴）是迄今为止人们观测到的最剧烈的高能天体物理现象，其剧烈程度可能仅次于宇宙大爆炸。自从20世纪60年代被发现以来，伽玛射线暴就以其短时标、高能量、远距离、复杂光变和谱态等显著特征而引起人们的广泛关注。半个世纪以来，伽玛射线暴研究领域在观测和理论两个方面都取得了许多令人瞩目的成就，但仍然有许多新老问题有待解决，比如前身星问题、中心引擎喷流的产生和加速机制，喷流的物质组分和结构等等。本文主要介绍了伽玛射线暴的观测进展和标准的火球激波模型，提出了一个建立在Blandford-Znajek机制和Blandford-Payne机制共存基础上的磁驱动双结构喷流模型。本文首先对伽玛射线暴的观测进展进行了介绍。回顾了各个历史时期主要的观测卫星在伽玛射线暴观测方面取得的重要发现，对伽玛射线暴的时变特征、谱形特征、伽玛暴的分类以及根据观测数据统计得到的一些经验关系进行了概括。其次，本文对伽玛射线暴的标准模型——火球激波模型——进行了比较详细的介绍。详细介绍了火球的概念、火球演化的动力学过程和激波辐射理论，最终给出一个用来解释伽玛射线暴瞬时辐射和余辉辐射的光变曲线和谱形特征的标准火球激波模型的较为清晰的轮廓。然后，本文对伽玛射线暴中心引擎喷流的磁驱动机制——主要是Blandford-Znjek和Blandford-Payne机制——进行了简要介绍，继而对建立在BZ机制和BP机制共存基础上双结构喷流模型做了初步的定量计算。在该模型中，中心喷流由Kerr黑洞的BZ机制驱动，其喷流物质来自于吸积盘内区，外围喷流由发生在吸积盘上的BP机制驱动。在假定大尺度磁场位形和盘物质吸积率随盘半径分布函数的基础上，本文推导了磁驱动双成分喷流的内外Lorentz因子的解析计算公式，，其中外围喷流（由BP机制驱动）的Lorentz因子取决于中心黑洞的自转、磁场位形以及盘风的强弱，中心喷流（由BZ机制驱动）的Lorentz因子取决于黑洞的自转以及盘内区物质进入中心喷流的比例。本文发现BZ喷流的Lorentz因子一般要比BP喷流的Lorentz因子大得多，这意味着BZ机制和BP机制可以做为双结构喷流的十分自然的起源。另外，通过对三个伽玛暴和三个活动星系核的双结构喷流的内外洛伦滋因子（Lorentzfactor）的拟合，本文发现这两类不同尺度天体的吸积盘可能有很大的不同，具体说来，活动星系核的吸积盘有很强的盘风，而伽玛射线暴中心引擎吸积盘的盘风则相对较弱。最后，对本文的主要内容和伽玛暴研究领域尚待解决的若干问题做了总结，对双结构喷流磁驱动模型的进一步细化做了展望。
[Abstract]:Gamma-ray burst (GRBs) is the most intense high-energy astrophysical phenomenon observed so far. Its intensity is probably second only to the Big Bang. Since its discovery in 1960s, gamma-ray bursts have been short-lived, high-energy, and long-range. Complex light variation and spectral state have attracted wide attention. In the past half century, many remarkable achievements have been made in both observation and theory in the field of gamma-ray bursts (GRBs). However, there are still many new and old problems to be solved, such as the predecessor star problem, the generation and acceleration mechanism of the central engine jet. This paper mainly introduces the observation progress of gamma ray bursts and the standard fireball shock wave model. A magnetically driven dual-structure jet model based on the coexistence of Blandford-Znajek mechanism and Blandford-Payne mechanism is proposed. In this paper, the observation progress of gamma-ray bursts is introduced, and the important findings made by the main observation satellites in each historical period are reviewed, and the time-varying characteristics of the gamma-ray bursts are also discussed. The spectral features, the classification of gamma-ray bursts and some empirical relationships based on observational data are summarized. Secondly, the standard model of gamma-ray bursts, the fireball shock model, is introduced in detail. The concept of fireball, the dynamic process of fireball evolution and the theory of shock radiation are introduced in detail. Finally, a clear outline of the standard fireball shock wave model, which is used to explain the phototropic curves and spectral characteristics of the instantaneous and afterglow radiation of gamma ray bursts, is given. And... In this paper, the magnetic driving mechanism of the GRB center engine jet, mainly the Blandford-Znjek and Blandford-Payne mechanisms, is briefly introduced. Then, the dual structure jet model based on the coexistence of BZ mechanism and BP machine is calculated. In this model, the central jet is driven by the BZ mechanism of Kerr black hole. The jet material comes from the inner area of the accretion disk, and the external jet is driven by BP machine which occurs on the accretion disk. On the basis of the assumption of the large scale magnetic field configuration and the distribution function of the mass accretion rate with the radius of the disk. In this paper, the analytical formula for the internal and external Lorentz factor of a magnetically driven two-component jet is derived, in which the Lorentz factor of the external jet (driven by a BP machine) is determined by the rotation of the central black hole. The configuration of the magnetic field and the strength of the disk wind. Central jet (driven by BZ mechanism). The Lorentz factor of BZ is determined by the rotation of the black hole and the ratio of the mass in the disk to the central jet. It is found that the Lorentz factor of the BZ jet is generally higher than that of the Lorentz factor of the BP jet. Son is much bigger. This means that BZ mechanism and BP machine system can be used as a very natural origin of dual-structure jet. The internal and external LorentzFactor of three gamma bursts and three active galactic nuclei were fitted. In this paper, we find that the accretion disks of these two kinds of objects with different scales may be very different. Specifically, the accretion disks of the active galactic nuclei have very strong disk winds, while the disk winds of the accretion disks of the center engine of the gamma ray bursts are relatively weak. Finally, the main contents of this paper and some problems that remain to be solved in the field of gamma-ray bursts are summarized, and the further refinement of the dual-structure jet magnetic drive model is prospected.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：P172.3

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