活动星系核中的软X射线超辐射起源

发布时间：2018-07-13 19:47

【摘要】：软X射线超是活动星系核(Active Galactic Nuclei,AGN)的重要组成部分，特别是I型的活动星系核(即吸积盘轴线与视线倾角小于90度的一类活动星系核)有着明显的软X射线超现象。活动星系核的辐射可以覆盖全波段，在X射线波段，1keV以下，辐射流量明显大于硬X射线波段(2-10keV)流量。同时，幂指数快速上升，从谱型上看会形成一个突起，这便是软X射线超。但是对于软X射线超的起源一直没能得到有效的解决。此前认为软X射线超如同大蓝包一样起源于吸积盘的辐射，但是根据经典的吸积盘理论，要使得吸积盘的辐射能够达到X射线波段的辐射就必须要让中心黑洞质量很小，同时吸积盘吸积率接近爱丁顿吸积率。但实际观测表明，发现存在明显软X射线超的源并没有严格服从这些条件，因此利用经典的吸积盘模型来解释软X射线超存在困难。同时，观测表明软X射线超对应黑体谱的温度稳定，，大致就在0.1-0.2keV附近。这个也是经典的吸积盘模型很难解释的。后继相续提出了很多模型对软X射线超进行解释，如吸收反射模型、Slim盘模型、盘风模型、热康普顿模型等。但是这些模型或多或少都会存在一些困难，并不是最佳的解释方案。对于软超的起源需要寻求其他的解决方案。磁场普遍存在于等离子体各种物理机制里面，因此我们将磁场考虑进软X射线超的起源很有必要。在吸积盘的较差转动以及湍流的作用下，磁场会不可避免的缠绕而产生磁重联。在磁重联的作用下，会产出激波，激波会使得吸积盘中的热电子加速转变成非热电子，这些非热电子会通过逆康普顿散射而冷却，同时释放出高能光子。我们考虑磁重联的能量转换很可能是软X射线超的起源。最后我们选择了25个具有明显软X射线超的源进行拟合，结果可以很好的拟合。
[Abstract]:Soft X-ray hyperthermia is an important part of Active Galactic Nucleus (AGN), especially the type I active galactic nuclei (i.e., a class of active galactic nuclei whose axis of accretion disk is less than 90 degrees of line of sight) has obvious soft X-ray hyperphenomena. The radiation of active galactic nuclei can cover the whole wave band, and the radiation flux below 1 Kev in the X ray band is obviously larger than that in the hard X ray band (2 to 10 Kev). At the same time, the power exponent rises rapidly, and a protuberance is formed from the spectrum form, which is called soft X ray super. However, the origin of soft X-ray superscript has not been effectively solved. It was previously thought that soft X-rays originated from the radiation of accretion disks just like big blue packets, but according to classical accretion disk theory, in order for accretion disk radiation to reach X-Ray band radiation, the mass of the central black hole must be very small. At the same time, the accretion rate of accretion disk is close to Eddington accretion rate. But the actual observation shows that there are obvious sources of soft X-ray superfluous which are not strictly satisfied from these conditions, so it is difficult to interpret soft X-ray superscript using classical accretion disk model. At the same time, it is shown that the temperature of the soft X-ray supercorresponding blackbody spectrum is stable, approximately in the range of 0.1-0.2 Kev. This is also the classical accretion disk model is very difficult to explain. Subsequently, many models are proposed to explain the soft X-ray superfluous, such as the absorption reflection model, the Slim disk model, the disk wind model, the hot Compton model, and so on. But these models are more or less difficult and are not the best way to explain them. Other solutions are needed for the origin of soft superpowers. The magnetic field exists in various physical mechanisms of plasma, so it is necessary to take the magnetic field into account of the origin of soft X-ray supersonic. Due to the poor rotation of the accretion disk and the effect of turbulence, the magnetic field will inevitably be wound and reconnected. Under the action of magnetic reconnection, shock waves will be produced, which will accelerate the conversion of hot electrons in accretion disk into non-hot electrons, which will cool by inverse Compton scattering and release high-energy photons. We consider that the energy conversion of magnetic reconnection is probably the origin of soft X-ray supersonic. Finally, 25 sources with obvious soft X-ray superscript were selected for fitting, and the results can be fitted well.
【学位授予单位】：中国科学院研究生院（云南天文台）
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P157.6;P172.2

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