Fermi Blazars光变类型的统计研究

发布时间：2018-11-09 07:33

【摘要】：活动星系核(Active Galactic Nucleus)的中心以一个超大质量的黑洞为引擎,周围是环绕着黑洞旋转的吸积盘。黑洞吸积周围的物质,将引力能转化为辐射能,由于吸积的物质具有角动量,下落的过程中会环绕黑洞形成吸积盘,吸积盘上发出光学、紫外、X射线等波段的辐射。在吸积盘两侧存在着相对论性喷流,喷流上几乎存在着各个波段的辐射。活动星系核有一个子类叫Blazar天体,由于观测者的视线方向与喷流的方向只有很小的夹角,所以观测上有一些极端的性质,如大幅度快速光变、高且变化的偏振、视超光速运动等。Blazars在观测上显示出不同变化时标,不同变化幅度混合的复杂光变,光变与天体内在的结构和机制相联系。对于如此复杂的变化,是需要引入统计方法对其进行定性和定量的分析。对光变的类型进行统计是一个很有意义的工作。前人在Blazar天体光变研究中,多集中在光变中的准周期信号,有一系列的周期被发现。也有很多研究者从另一个角度出发,发现Blazars天体的光变曲线在频域上服从幂律,类似于红噪声,但没有进一步的深入研究。在此工作中,采用了最简单的红噪声模型—布朗噪声或高斯过程,来检验Blazars天体的光变曲线是否与之相类似。在具体做法上,第一步采用K-S检验来比较130个源的每日流量变化的分布与高斯分布是否一致,结果表明大多数源的每日流量变化分布与高斯分布相同的置信度小于1%,说明光变可能与Blazar天体的内部物理机制有关;第二步将任意两个源的每日流量变化分布用K-S检验进行比较,发现有些源之间的分布很相似,说明那些相类似的源之间可能有相同的物理机制;由于的每日流量变化分布与高斯分布不相似,所以第三步检验了分布两翼的偏差,发现负的每日流量变化的分布比正的每日流量变化的分布要更平坦,这说明负的部分弥散比正的部分大,即负的部分,流量变化的尺度时大时小,而正的部分,流量变化的尺度基本差不多;第四步计算了分布的偏度和峰度,发现峰度随着偏度的增加而增加。
[Abstract]:The center of the AGNs (Active Galactic Nucleus) is a supermassive black hole, surrounded by accretion disks orbiting the black hole. The matter around the accretion of the black hole is converted into radiation energy. Because the accretion material has angular momentum, it will form accretion disk around the black hole in the process of falling. The accretion disk emits optical, ultraviolet and X-ray radiation. There are relativistic jets on both sides of the accretion disk. The active galactic nucleus has a subclass called the Blazar object. Because the observer has only a very small angle of view to the direction of the jet, there are some extreme properties in the observations, such as large, fast light changes, high and varying polarization. The apparent superluminal motion and so on. The observation of Blazars shows that the complex light variation with different time scales and different variation amplitude is related to the inner structure and mechanism of the celestial body. For such complex changes, it is necessary to introduce statistical methods to analyze them qualitatively and quantitatively. It is a meaningful job to count the types of light change. In the study of Blazar celestial light variation, most of the quasi-periodic signals are concentrated in the light variation, and a series of periods have been discovered. From another point of view, many researchers have found that the optical variation curve of Blazars objects obeys the power law in frequency domain, similar to Yu Hong noise, but there is no further study. In this work, the simplest red noise model-Brownian noise or Gao Si process is used to test whether the optical curve of Blazars objects is similar to it. In the specific practice, the first step is to use K-S test to compare whether the distribution of daily flow changes of 130 sources is consistent with that of Gao Si. The results show that the daily flow variation distribution of most sources is the same as that of Gao Si, and the confidence level is less than 1. It is suggested that the light variation may be related to the internal physical mechanism of Blazar objects. In the second step, the distribution of daily flux of any two sources is compared with K-S test, and it is found that the distribution of some sources is very similar, which indicates that there may be the same physical mechanism among those similar sources. Since the distribution of daily flow changes is not similar to that of Gao Si, the third step examines the deviation of the two wings of the distribution, and finds that the distribution of the negative daily flow changes is more flat than that of the positive daily flow changes. This shows that the negative part is larger than the positive part, that is, the negative part, the scale of flow change is large and small, and the positive part, the scale of flow change is almost the same; In the fourth step, the skewness and kurtosis of the distribution are calculated, and it is found that the kurtosis increases with the increase of skewness.
【学位授予单位】：广州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P145.8;P157.6

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