对脉冲星射电辐射束模型的观测检验

发布时间：2018-03-14 16:29

本文选题：脉冲星　切入点：辐射束模型　出处：《广州大学》2016年硕士论文　论文类型：学位论文

【摘要】：脉冲星的射电辐射束结构不仅关系到脉冲星的射电辐射机制,也关系到和脉冲星族群有关的理论研究以及与脉冲星探测率有关的观测研究,但是长久以来,射电辐射束的结构一直存在争议。目前主要有三种理论或经验模型——锥模型、扇形束模型和斑块模型。以往对模型的观测检验均限于小样本,主要原因是对于确定辐射束参数的两个基本量——磁倾角和撞击角,过去能从观测中定出的比较少。随着观测资料不断增加和近几年国际上高质量观测数据的释放,进行大样本检验成为可能。磁倾角和撞击角可以通过使用旋转矢量模型(RVM)拟合线偏振位置角数据得到。为了克服传统的Levenberg-Marquardt非线性拟合和格点搜寻算法的低效、易过拟合等问题,本文发展了一套基于贝叶斯推断并用马尔可夫链蒙特卡洛(MCMC)实现的拟合算法。对欧洲脉冲星轮廓数据库中全部的偏振观测数据进行了筛选,最终成功拟合得到了123颗脉冲星的磁倾角和撞击角参数,结合前人给出的64颗脉冲星的结果,我们得到了当前国际上最大的有磁倾角和碰撞角参数的脉冲星样本。利用上述123颗脉冲星的参数,本文进行了迄今最大样本的辐射束模型检验。通过检查碰撞角和累积脉冲轮廓宽度数据的关系,并与扇形束模型和锥模型理论预言的关系进行比对,我们发现观测数据支持扇形束模型,不支持锥模型。这对于目前流行的锥模型提出了挑战。本文发展出的MCMC算法具有高效、不易过拟合、能合理估计参数不确定度的特点,在未来可与FAST和SKA相关研究结合,进行更大样本的RVM模型参数拟合。本文所得到的磁倾角和碰撞角对脉冲星辐射几何、辐射机制、族群和演化等方面的研究有应用价值。
[Abstract]:The radio radiation beam structure of pulsar is not only related to the radio radiation mechanism of pulsar, but also related to the theoretical study of pulsar population and observation research related to pulsar detection rate. But for a long time, The structure of radio radiation beam has always been controversial. At present, there are three kinds of theoretical or empirical model-cone model, sector beam model and patch model. The main reason is that the two basic quantities of determining the parameters of the radiation beam magnetic dip angle and impact angle can be determined less from the observation in the past. With the increasing observation data and the release of the international high quality observation data in recent years, It is possible to test large samples. Magnetic dip angle and impact angle can be obtained by using rotation vector model to fit linear polarization position angle data. In order to overcome the problems of low efficiency and easy over-fitting of traditional Levenberg-Marquardt nonlinear fitting and lattice search algorithms, In this paper, a fitting algorithm based on Bayesian inference and Markov chain Monte Carlo (MCMC) algorithm is developed. All polarization observations in the European pulsar profile database are screened. Finally, the parameters of magnetic inclination and impact angle of 123 pulsars are obtained successfully, and the results of 64 pulsars given by predecessors are combined. We have obtained the largest sample of pulsars in the world at present with the parameters of magnetic inclination and collision angle, using the parameters of the above 123 pulsars, In this paper, the radiation beam model of the largest sample to date has been tested. By examining the relation between the collision angle and the data of cumulative pulse profile width, and comparing it with the relation predicted by the sector beam model and the cone model theory, We find that the observed data support sector beam model, not cone model. This challenge to the popular cone model. The MCMC algorithm developed in this paper has the characteristics of high efficiency, not easy to fit, and can reasonably estimate the uncertainty of parameters. In the future, it can be combined with FAST and SKA to fit the parameters of RVM model with larger sample. The magnetic inclination and collision angle obtained in this paper are valuable for the study of radiative geometry, radiation mechanism, population and evolution of pulsar.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P145.6;P162

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