基于谱分析的Blazar天体光变周期研究

【作者】 唐洁；

【导师】 伍林； 张雄；

【作者基本信息】 云南师范大学 ， 天体物理， 2007， 硕士

【摘要】 活动星系核AGNs (Active Galactic Nucleus)是中心区域有大能量辐射的一类特殊的星系。活动星系核的一些重要性质包括：它们具有恒星状的外表,随时间变化的连续光谱,以及宽的发射线等等。光变是活动星系核的普遍现象,从射电到X射线的所有波段都观测到了活动星系核的光变。光变对活动星系核中心区域的物理机制和理论模型作了有力的限定。Blazar天体是射电噪AGNs,在所有的AGNs中光变时标最短,它们也是宇宙中产能最大、光变最剧烈的天体。目前标准的活动星系核统一模型认为：AGNs的中央有一个大质量黑洞,环绕该黑洞的是一个吸积盘,射电强活动星系核还会在吸积盘的旋转轴方向产生一对双向的相对论性喷流。Blazar的喷流与我们观测视线的夹角很小,喷流的辐射经过Doppler效应增强后,产生了一个下至射电波段、上至高能y-ray波段的很宽的频谱。研究Blazar天体能量的起源、传输和变化对宇宙学以及基本物理学都有重要的意义。探索Blazar光变资料中的周期或准周期变化是一个有待深入研究的领域。由于光变资料的复杂性,目前寻找周期的算法还显得不够完善。在本论文的后半部分作者详细讨论了几种有用的周期寻找方法。本文综述了活动星系核的基本性质和辐射机制。介绍了Blazar天体的光学观测和数据处理方法。讨论了Blazar天体的光变特性,以及光变对了解活动星系核本质的重要意义。并把经典谱估计法和现代谱估计法应用到类星体3C 279、3C 345,BL Lac天体OJ 287、ON 231的光变周期分析中,得到它们的光变周期分别为7.14年、10.00年、11.76年、6.80年。比较了各种估计方法性能之优劣,便于在实际工作中做出正确选择。获得的周期对进一步研究它们的物理机制很有帮助。更多还原

【Abstract】 Active galactic nucleus, or AGNs, are peculiar galaxies which have energetic phenomena in the central regions. Some of the most important properties of AGNs are that they are star-like objects, have time-variable continuum spectra and broad emission lines. Variability is a common phenomenon in AGNs and is observed over wide range from radio to X-ray. It provides a powerful tool for constraining the physical mechanisms and models of the central regions of AGNs.Blazars are radio-loud active galactic nucleus. The timescale of them is shortest in all AGNs. At the same time, they are the most powerful and the largest amplitude variable objects in the cosmos. According to the standard unified model of AGNs, there is a central massive black hole, surrounded by an accretion disk. A powerful reletivistic jet will emanate from the region near the black hole. The viewing angle of the jet of Blazar is very small. Thus, its radiation will be Doppler enhanced, and generate a wide spectrum from radio band to hight energyγ-ray band. To study Blazars energy originates, transfers and variates is very important to cosmology and basic physics.The periodicity analysis of the light curves of Blazars needs improvement. Due to the complication of Blazars’light curves, the present periodicity analysis methods are not perfect. In the rest part of this dissertation, I disscussed in detail some suitable periodicity analysis methods.The properties and radiation mechanisms of AGNs were reviewed. The methods of data processing and optical observation of Blazars were introduced. Then, the characteristic of Blazars variability and significance of variability for understanding the nature of AGNs were discussed. The methods that are classical spectrum estimation methods and modern spectrum estimation methods have been applied to analyze the period of the Blazar 3C 279,3C 345 and BL Lac Objects OJ 287, ON 231. Their periods are 7.14yr、10.00yr、11.76yr and 6.80yr. Moreover, their advantages and disadvantages are discussed for the practical applications. The obtained periods are helpful to understand their physical mechanisms.更多还原