伽玛暴及其它天体过程中的偏振研究

发布时间：2018-05-12 23:38

本文选题：伽玛暴 + 偏振　；参考：《南京大学》2016年博士论文

【摘要】：伽玛暴是来自宇宙深处的剧烈的爆发现象。其辐射分为两个阶段,首先看到的是瞬时辐射,随后会观测到余辉。瞬时辐射的光变曲线非常复杂,通常由一个或多个脉冲组成。瞬时辐射的谱通常有Band谱来描述。余辉的光变相对简单,通常由分段的幂律来描述。科学家提出了瞬时辐射的内激波模型和余辉的标准模型。随着观测的进行,瞬时辐射和余辉的观测都呈现出多样的观测特点。不同的模型也被相继提出来,用于解释多样的观测。伽玛暴的辐射机制通常被认为是同步辐射。而同步辐射是高度偏振的。随着偏振观测技术的发展,现在已经有一些仪器在进行偏振观测,如LT,VLT,和INTEGRAL等等。偏振观测可用于研究源中的磁场,源的几何结构等性质。本论文主要围绕伽玛暴及其它天体物理过程中的偏振性质展开。第一章是伽玛暴领域尤其是偏振研究领域的综述,主要介绍的是伽玛暴及其余辉的主要观测性质和理论解释,尤其是其中的偏振的观测和理论研究。内容包括瞬时辐射的观测和理论模型(主要有内激波模型,ICMART模型和耗散光球模型),余辉的观测和理论模型(余辉的标准模型,早期正反激波模型,统一动力学模型,其它动力学模型,能量注入模型,同步自康普顿散射模型),瞬时辐射和余辉中的偏振观测,偏振的理论模型(随机磁场中的同步辐射模型,规则磁场中的同步辐射模型,逆康普顿散射模型以及有结构的喷流模型),以及其它天体物理过程(快速射电暴,超新星和活动星系核)中的偏振。第二章到第五章是本人在偏振方面的工作。第二章研究的是伽玛暴早期余辉中偏振性质。在这一章中,以统一动力学模型为基础,我们推导了一个包含反向激波的动力学模型,这个动力学模型也可以从早期相对论阶段演化到晚期的非相对论阶段。之后,在两种磁场构型下,我们计算了早期光学余辉的偏振演化。如果偏振方位角逐渐改变其值或者偏振方位角突然改变90度时对应的偏振度非0,则可推断3区的磁场为平行场,对应的中心引擎为磁星。如果偏振方位角突然改变90度时对应的偏振度为0,则3区的磁场可能为环形场,对应的中心引擎可能是黑洞。我们用本章中的模型拟合伽玛暴GRB120308A的光变曲线和偏振演化,发现两个磁场构型都能拟合该暴的观测数据,因此对于这个暴,我们并不能区分它的中心引擎是磁星还是黑洞。第三章研究的是伽玛暴晚期光变曲线中的平台期的偏振演化,并以此来区分两个主流模型。大约一半的伽玛暴X射线余辉中观测到了平台期。有两个主流模型可以解释这个观测现象,分别是相对论星风泡模型和结构化的抛出物模型。相对论星风泡模型的中心引擎为毫秒磁星,晚期的能量注入为Poynting流,其中的磁场构型为平行场。而结构化的抛出物模型的中心引擎为转动的黑洞,主要的注入能量为动力学能量,是否有规则磁场残留尚不清楚。我们知道对于结构化的抛出物模型,通常只有一个能段有平台期。但是对于相对论星风泡模型,平台期在光学和X射线波段都会有。我们的计算结果显示,如果是相对论星风泡模型,在平台期偏振度的演化会有一个鼓包,而结构化的抛出物模型中并没有这样的结构。因此,从平台期的偏振度观测我们可以区分两个模型。第四章研究的是双成分喷流模型下的伽玛暴的光学余辉的偏振性质。伽玛暴的一类中心引擎是黑洞加吸积盘系统。黑洞由于吸积物质会产生喷流。其中,一个是由于Blandford-Znajek机制产生的窄喷流,另一个是由盘产生的宽喷流。因此,窄喷流中的磁场构型就是环形的,而宽喷流中没有有序磁场。在我们取的参数下,早期余辉的光变由窄喷流主导,晚期余辉的增亮现象由宽喷流主导。早期的偏振度在某些观测角度处有鼓包。第五章研究的是进动喷流的辐射的偏振性质。这章的工作还在继续。先介绍一下初步的结果。黑洞加吸积盘系统可能是很多天文现象的中心引擎。如果黑洞的自转轴和盘的转轴不平行,则由黑洞驱动的或由盘驱动的喷流就会有进动的现象。我们的研究显示这样的进动的喷流的辐射和偏振的演化都有周期性的变化。最后在第六章我们总结伽玛暴的瞬时辐射和余辉的偏振的观测特点,以及偏振的理论模型。从偏振观测,我们可以区分不同的中心引擎和喷流的组份。从X射线余辉平台的偏振观测还可以区分两个平台期的主流模型。从偏振观测还能得到源的哪些物理信息还有待进一步的研究。
[Abstract]:The gamma storm is a violent eruption from the depths of the universe. Its radiation is divided into two stages. First, the instantaneous radiation is seen. The afterglow will be observed. The light curve of the instantaneous radiation is very complex, usually composed of one or more pulses. The spectrum of the instantaneous radiation is usually described by the Band spectrum. The scientists put forward the internal shock model of instantaneous radiation and the standard model of afterglow. With the observation, the observations of instantaneous radiation and afterglow have varied observation features. Different models are also proposed to explain various observations. The radiation mechanism of the gamma storm is usually considered to be synchronous. Radiation. And synchrotron radiation is highly polarized. With the development of polarization observation technology, there have been some instruments in the polarization observation, such as LT, VLT, and INTEGRAL. Polarization observation can be used to study the magnetic field in the source, the geometrical structure of the source and so on. This paper focuses on the polarization properties of the gamma storm and other astrophysical processes. The first chapter is a summary of the field of gamma storm, especially in the field of polarization, mainly introducing the main observational properties and theoretical explanations of the gamma storm and its afterglow, especially the observation and theoretical study of the polarization, including the observation and theoretical model of the instantaneous radiation (the main need for the internal shock model, the ICMART model and the dissipative light sphere) Model), the observation and theoretical model of afterglow (standard model of afterglow, early positive and negative shock model, unified dynamic model, other dynamics model, energy injection model, synchronous self Compton scattering model), instantaneous radiation and Yu Huizhong polarization observation, polarization theory model (synchrotron radiation model in random magnetic field, regular magnetic field) The synchrotron radiation model, the inverse Compton scattering model and the structured jet model, and the polarization in other astrophysical processes (rapid radio storm, supernova and active galactic nucleus). The second chapter to the fifth chapter is the work of polarization. The second chapter studies the polarization properties in the early afterglow of the gala storm. On the basis of a dynamic model, we derive a dynamic model containing the reverse shock wave, which can also evolve from the early relativistic stage to the late non relativistic stage. Then, under the two magnetic configurations, we calculate the polarization evolution of the early optical afterglow. If the azimuth angle of polarization gradually changes its value. Or the degree of polarization of the polarizing azimuth suddenly changes 90 degrees, and the corresponding degree of polarization is not 0, then it can be deduced that the magnetic field in the 3 region is parallel and the corresponding center engine is a magnetic star. If the degree of polarization of the polarization azimuth suddenly changes 90 degrees is 0, then the magnetic field in the 3 region may be a ring field, and the corresponding center engine may be a black hole. The light curve and polarization evolution of the gamma ray storm GRB120308A show that two magnetic configurations can fit the observation data of the storm, so we can not distinguish between the magnetic stars or the black holes for this storm. The third chapter studies the polarization evolution of the platform period in the late gamma ray curve of the gamma storm, and thus distinguishes two. The mainstream model. About half of the gamma ray X ray afterglow observed in the platform period. There are two main models to explain the observation phenomenon, namely the relativistic star bubble model and the structured ejecta model. The center engine of the relativistic star bubble model is millisecond magnetic star, and the energy injection into the Poynting flow at the late stage, the magnetic field in it. The structure is a parallel field. The central engine of the structured projectile model is a rotating black hole. The main injection energy is kinetic energy. It is not clear whether there is a regular magnetic field residual. We know that there is only one stage for a structured projectile model, but for the relativistic bubble model, the platform is in the light. Our calculations show that if it is a relativistic bubble model, there is a drum in the evolution of the degree of polarization in the platform period, and there is no such structure in the structured model. Therefore, we can distinguish two models from the degree of polarization of the platform period. The fourth chapter studies the dual component spray. The polarization properties of the optical afterglow of a gamma storm under the flow model. A type of central engine of a gamma storm is a black hole plus accretion disk system. A black hole produces a jet due to accretion. One is a narrow jet produced by the Blandford-Znajek mechanism and the other is a wide spout produced by the disk. Therefore, the magnetic configuration in the narrow jet is a ring. There is no orderly magnetic field in the wide jet. Under the parameters we take, the light change of the early afterglow is dominated by the narrow jet. The brightening phenomenon of the late afterglow is dominated by the wide jet. The initial degree of polarization has a drum in some observation angles. The fifth chapter is the study of the radiating properties of the precession jet. The work of this chapter is still continuing. First, the first introduction of the first introduction The black hole plus accretion disk system may be the central engine of many astronomical phenomena. If the rotation axis of the black hole is not parallel to the rotating axis of the disk, the black hole driven or disk driven jet will have the precession phenomenon. Our study shows that the radiation and polarization evolution of such a precession are periodic changes. Finally, in the sixth chapter, we summarize the observation characteristics of the instantaneous radiation and the polarization of the afterglow of the gamma storm, as well as the theoretical model of polarization. From the polarization observation, we can distinguish between the different central engines and the components of the jet. From the polarization observation of the X ray afterglow platform, we can distinguish the main model of the two platform period. It remains to be further studied which physical information of source.

【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P172.3

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