高能辐射机制与伽玛射线暴瞬时辐射的研究

发布时间：2018-06-21 00:06

本文选题：伽玛射线暴 + 高能辐射机制　；参考：《南京大学》2013年博士论文

【摘要】：伽玛射线暴(简称伽玛暴)是宇宙中最为猛烈的高能爆发,它是一种随机出现的短时标脉冲式现象,自20世纪60年代被Vela卫星发现以来,一直都是天体物理学家所关注的研究热点。1997年BeppoSAX卫星首先发现了伽玛暴的余辉,后来又帮助测定了伽玛暴的红移,因而确定伽玛暴是起源于宇宙学距离上的现象。现在通常认为,持续时标长于2s的长暴起源于大质量恒星的坍缩,而时标短于2s的短暴来自双致密星的并合。对伽玛暴的研究可以帮助人们了解极端相对论、极端高能条件下的物理过程,也可以帮助其他领域的研究,如限制宇宙学模型等。本文讨论的是伽玛暴可能的辐射机制以及瞬时辐射的光变曲线。由于辐射机制与瞬时辐射与爆发的中心能源直接相关,因此对它们的研究可以帮助更好地了解中心能源的一些特性。第一章回顾了伽玛暴的发现和研究史,简要总结了Compton伽玛射线天文台、BeppoSAX卫星、Swift卫星、Fermi伽玛射线太空望远镜等重要的伽玛暴监测卫星得出的成果,并总结了伽玛暴瞬时辐射与余辉的多波段观测特性。第二章介绍了当前的伽玛暴标准模型,即中心能源抛射出火球,火球内部速度不同的壳层彼此碰撞,产生内激波,将火球定向运动动能转化为内能,最终转化为非热辐射,产生瞬时辐射；火球与外部介质相互作用,产生正反外激波,形成观测到的余辉。在此框架下,我们介绍了火球的特性、激波的演化、可能的辐射机制以及一些后标准效应,并对中心能源作了简要介绍。另外由于瞬时辐射的内激波模型仍旧存在很多难以解决的问题,我们还介绍了其他几种可能的瞬时辐射模型,包括电磁模型、湍流模型、内部碰撞诱发磁重联与湍流模型(ICMART)等。我们在第三章给出了洛仑兹因子以幂律分布的相对论性电子产生的同步曲率自康普顿(SCSC)辐射的能谱。来自相对论性电子环绕弯曲磁力线运动的同步曲率辐射及其自康普顿散射是伽玛暴环境下可能的辐射机制。我们发现,如果磁场的曲率半径以及电子的回旋半径都具备适当的取值,同步曲率自康普顿辐射的能谱与同步自康普顿或曲率自康普顿辐射都存在较大差异。为了得到更加精确的图像,我们还讨论了电子的冷却、电子漂移、种子谱低能自吸收以及散射谱高能Klein-Nishina截断导致的影响。我们以伽玛暴作为我们的讨论背景。所得的结果可以被看作是相对论性电子在弯曲磁力线环境下发生自康普顿散射的统一图像,可以用于描述许多天体物理现象,包括活动星系核(AGN)、脉冲星,也包括伽玛暴。我们在第四章中模拟了ICMART模型框架下伽玛暴的瞬时辐射光变曲线。这一模型适用于辐射区的磁化因子σ较大但是又不太大的情形。我们证明,这一模型可以产生变化较大的光变曲线,它具备快慢两种成分。σ较大的抛射物中湍动磁重联的过程会产生诸多的小型辐射元,这些小辐射元被局域多普勒增亮的结果就是快速光变。每个ICMART事件磁重联随时间的雪崩式失控增长以及随后小型辐射元的枯竭定义了宽阔的慢成分。一个伽玛暴的光变曲线通常由数个ICMART事件组成,它们由中心能源的不规则活动驱动。通过改变模型的参数,包括包括初始洛伦兹因子、重联区取向和长度分布、喷流张角、辐射区半径、观测能段等,就可以产生观测所见形态与功率谱(PDS)各不相同的光变曲线了。我们还讨论了这些参数对PDS产生的影响。最后我们在第五章进行了讨论,并列出了一些有待解决的问题以及即将入役的观测仪器。另外我们在附录A与附录B中分别列出了对同步曲率辐射以及ICMART模型一些问题的具体推导。
[Abstract]:Gamma - ray bursts ( called gamma - ray bursts ) are the most violent outbreaks in the universe . It is a random short - term pulse phenomenon . Since the discovery of Vela satellites in the 1960s , it has been the focus of astrophysicists .

This paper discusses the possible radiation mechanism of gamma - ray and the curve of transient radiation . Since the radiation mechanism is directly related to the instantaneous radiation and the central energy source of the outbreak , the research of them can help to better understand some of the characteristics of the central energy source . Chapter one reviews the discovery and research history of the Gamma - ray Observatory , summarizes the results of the important gamma - ray monitoring satellites such as the compton gamma - ray observatory , the Beppo4 satellite , the Swift satellite , the Fermi - gamma - ray space telescope and the like , and summarizes the multi - band observation characteristics of the gamma - ray instantaneous radiation and afterglow .

The second chapter introduces the current standard model of gamma storm , that is , the center energy is thrown out of the fireball , the shell layers with different velocities inside the fireball collide with each other , the internal shock wave is generated , the kinetic energy of the directional motion of the fireball is converted into the internal energy , and finally converted into non - thermal radiation to generate instantaneous radiation ;
In this framework , we introduce the characteristics of fireballs , the evolution of shock waves , the possible mechanism of radiation and some post - standard effects , and introduce some other possible transient radiation models , including electromagnetic models , turbulence models , internal collision - induced magnetic reconnection and turbulence models ( ICMART ) .

In chapter 3 , we give the energy spectrum of the synchrotron curvature from the relativistic electron generated by relativistic electron with power law distribution . The synchronous curvature radiation from relativistic electrons around bending magnetic lines and its self - compton scattering are the possible radiation mechanisms . We also discuss the effects of electron cooling , electron drift , low energy self - absorption and high - energy Klein - Nishina truncation . We also discuss the phenomena of electron cooling , electron drift , low energy self - absorption and scattering spectrum high - energy Klein - Nishina truncation .

In chapter 4 , we simulate the transient radiative decay curve of gamma - ray in the framework of ICMART model . The model is suitable for the case of larger but less magnetic factor . We prove that this model can produce many small radiating elements .

In conclusion , we discussed in Chapter V and listed some issues to be resolved and the instruments to be observed . We also listed in Appendix A and Appendix B a detailed derivation of some of the problems with simultaneous curvature radiation and ICMART models , respectively .
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：P172.3

【共引文献】