伽马暴X射线余辉研究与Fermi LAT未证认源的统计分类

发布时间：2018-01-11 21:21

本文关键词：伽马暴X射线余辉研究与Fermi LAT未证认源的统计分类　出处：《华中师范大学》2013年博士论文　论文类型：学位论文

【摘要】：本文的研究内容属于伽马射线天文学的范畴。近年来,随着伽马射线空间和地面望远镜的更新升级以及与其它多波段观测的紧密结合,伽马射线天文学取得了极大发展,其研究领域也被大大拓宽。本文的研究主要包括两个部分,一是对伽马暴X射线余辉的理论研究,二是对一些未证认的Fermi伽马射线稳态源的统计分类。伽马暴是伽马射线天文学研究的主要对象之一。自1967年发现至今,经过数十年的研究人们对伽马暴的认识已较为深入。但是,伽马暴的中心能源问题仍然是一个未解之谜。近年来,Swift卫星观测到伽马暴X射线余辉新特征(主要包括早期余辉的缓慢衰减和X射线耀发现象)为人们了解伽马暴的中心能源机制提供了重要线索。在标准外激波余辉模型下,这些X射线余辉新特征无法得到有效解释。因此,本文第一个研究工作将主要针对这一问题。为了有效解释X射线余辉的早期变平现象,一般认为伽马暴的中心致密天体很可能是一颗高速旋转的磁星,它可能在很长一段时间内为外激波注入能量。但是,本文认为,磁星能量的释放实际上很可能是通过携带了大量正负电子对的Poynting流的形式。而由于磁重联的原因,Poynting流有可能在追上伽马暴外激波之前就已经转化为相对论性的正负电子对星风。因此,星风与伽马暴抛射物质相互作用产生的终止激波将直接导致很强的X射线余辉辐射,甚至完全超过伽马暴外激波的辐射(即使有部分能量注入)。我们的数值计算结果显示,在星风磁化率满足一定条件的时候,这种情况是完全可能发生的。因此,我们提出某些观测到的伽马暴X射线余辉有可能直接来源于磁星星风终止激波的辐射,而不是传统的外激波。一定程度上讲,磁星星风终止激波辐射可被认为是一种内耗散起源的余辉辐射机制。 2008年以来,Fermi卫星的LAT探测器观测到了大量的稳态伽马射线源,这些源的属性是人们所关心的一个重要问题。Fermi合作组的证认结果显示,2年时间内观测到的1873个源中,有127个源的性质被完全确定,另有1171个源和候选对应体成协,但是剩下575个源未找到候选对应体。本文第二个工作就是对这575个未证认的源进行统计分类研究。和具体去找候选对应体的证认方法不同,我们这里并不是对单个源进行分析,而是选取反映未证认源的物理性质的观测量进行统计分析,其中包含空间分布、谱指数和光变指数。通过和已证认的源进行比较研究,讨论这575个未证认源的可能候选对应体。我们的统计分析结果显示,这些未证认源可能主要包括：超新星遗迹/脉冲星风星云,蝎虎座BL天体,射电平谱类星体和其他类型的活动星系,它们的比例分别为25%,29%,41%和5%。
[Abstract]:In recent years, with the updating and upgrading of gamma ray space and ground telescopes and the close integration with other multi-band observations, the research contents of this paper belong to the field of gamma ray astronomy. Gamma-ray astronomy has made great progress, and its research field has been greatly broadened. This paper mainly includes two parts, one is the theoretical study of X-ray afterglow of gamma-ray storms. The second is the statistical classification of some unauthenticated Fermi gamma ray steady-state sources. Gamma-ray storm is one of the main objects of gamma ray astronomy. Since its discovery in 1967, after decades of research people have been more in-depth understanding of gamma storms. The central energy problem of gamma storms remains an unsolved mystery in recent years. New characteristics of X-ray afterglow of gamma-ray storms observed by Swift satellite (mainly including slow decay of early afterglow and X-ray luminescence). It provides an important clue for people to understand the central energy mechanism of gamma storms, under the standard external shock afterglow model. These new characteristics of X-ray afterglow can not be effectively explained. Therefore, the first study in this paper will focus on this problem, in order to effectively explain the early flattening phenomenon of X-ray afterglow. It is generally believed that the central dense object of the gamma storm is probably a high speed rotating magnetic star which may inject energy into the external shock waves for a long time. The release of energy from magnetic stars may in fact be in the form of a Poynting stream that carries a large number of positron and negative electron pairs, and due to magnetic reconnection. The Poynting current may have been transformed into relativistic positron to star winds before catching up with the external shock waves of gamma storms. The terminating shock produced by the interaction between the starwind and the gamma ray ejection will directly lead to strong X-ray afterglow radiation. Even beyond the radiation of the external shock wave (even if there is partial energy injection), our numerical results show that when the susceptibility of the star wind meets certain conditions. Therefore, we suggest that some observed X-ray afterglow of gamma storms may be directly derived from the radiation of the magnetic star wind terminating shock waves. To some extent, the termination of shock wave radiation by magnetic star wind can be considered as a mechanism of afterglow radiation from the origin of internal dissipation. Since 2008, a large number of steady state gamma ray sources have been observed by the LAT detector of the Fermi satellite. The attributes of these sources are an important issue of concern. The results of the Fermi team's identification show that 127 of the 1 873 sources observed in the 2-year period have been fully identified. In addition, there are 1171 source and candidate counterpart consortia. However, the remaining 575 sources have not found candidate correspondence. The second work of this paper is to study the 575 unauthenticated sources by statistical classification, which is different from the method of identifying candidates. We do not analyze a single source here, but select observations reflecting the physical properties of unauthenticated sources for statistical analysis, including spatial distribution. Spectral index and photovariation index. By comparing with the identified sources, we discuss the possible candidates for these 575 unauthenticated sources. Our statistical analysis results show that: 1. These unidentified sources may include: supernova remnants / pulsar winds nebulae, BL objects in the constellation Scorpius, emissive spectrum quasars and other types of active galaxies, which account for 25% or 29% respectively. 41% and 5.
【学位授予单位】：华中师范大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：P172.3

【共引文献】