Blazars高能伽马射线的起源

发布时间：2018-05-05 08:15

本文选题：BL + Lac天体　；参考：《中国科学院研究生院（云南天文台）》2014年硕士论文

【摘要】：blazars是一类特殊的活动星系核（AGNs），它们的辐射被认为起源于与我们视线方向夹角很小的相对论性喷流。它们通常表现出快速的光变、高的偏振以及强的非热辐射。blazars的光谱能量分布（SEDs）通常由两个比较宽的成分组成：一个是低能成分，从射电到X射线波段，另一个是高能成分，从X射线到伽马射线波段。普遍认为它们SEDs的低能成分由相对论电子的同步辐射产生。然而高能成分的起源目前仍然存在争议。两类模型被用于解释blazarsSEDs的高能成分：轻子模型和强子模型。轻子模型认为blazars的高能辐射由电子与背景光子的逆康普顿散射过程产生。强子模型则认为blazars的高能辐射起源于质子的同步辐射或者光子强子相互作用。我们从轻子模型和强子模型两个方面研究了blazars高能伽马辐射的起源，主要的结果是： 1.我们研究了21个具有准同步SEDs的平谱射电类星体（FSRQs）伽马射线辐射区的位置。我们提出了一种限定伽马射线辐射区的方法。如果伽马射线辐射区在宽线区之内，逆康普顿（IC）散射发生在KN区域，伽马射线谱应该比光学近红外谱更陡。如果伽马射线辐射区在宽线区之外，IC散射发生在Thomson区域，伽马射线谱的谱指数应该与光学近红外谱的谱指数相同。为了测试我们的理论，我们用一区的轻子模型包括同步自康普顿（SSC model）和外康普顿模型（EC model）拟合了21个FSRQs准同步的SEDs，我们认为X射线辐射由SSC过程，GeV辐射来自于EC过程，其中EC辐射可能起源于相对论电子IC散射吸积盘和BLR的辐射或者是尘埃环的辐射。我们根据谱型和SEDs的拟合结果猜测5个FSRQs的GeV辐射区在宽线区之内，其它16个在宽线区之外。我们的SEDs拟合表明在21个FSRQs喷流中磁场和电场的能量密度接近均分。 2.我们用具有电子加速的SSC模型研究了Mrk421在2008年6月68日期间X射线和伽马射线的爆发活动。观测发现X射线和伽马射线明显相关，然而光学和X射线波段并不明显相关。我们认为Mrk421的辐射可能起源于两个不同的成分。一个是在外部区域的稳定成分，它主要产生光学辐射，在这个区域电子被一阶Fermi加速过程加速，我们用稳态的电子谱来产生这一区域的SSC辐射。另一个是在内部区域的变化成分，在这个区域电子被随机加速过程加速，我们用一个含时的SSC模型来产生这一区域的辐射。我们认为爆发是由随机加速过程导致电子谱变硬引起的，电子谱的变硬将会引起X射线和伽马射线谱的变硬。此外我们发现在两个区域中磁场和电子的能量密度都接近均分。 3.来自于遥远blazars非常硬的伽马射线谱挑战了标准的SSC模型。硬的伽马射线谱可能表明了存在一个高于SSC辐射的谱成分。我们研究了1ES1101232非常硬的伽马射线谱的可能起源。H.E.S.S.的观测表明VHE流量在任一时标内都不存在明显的光变。因此我们认为blazar1ES1101232硬的伽马射线谱可能起源于高能质子的辐射。我们提出了一个解释blazar1ES1101232硬的伽马射线谱的模型。在这个模型中，光学和X射线的辐射来自于原初电子和次级电子的同步辐射，GeV辐射由SSC过程产生，然而非常硬的伽马射线起源于中性π0的衰变，其中中性π0由高能质子与喷流内同步辐射光子发生pγ相互作用产生。我们的模型能够很好地解释1ES1101232的多波段能谱，，尤其是1ES1101232非常硬的伽马射线谱。为了通过pγ相互作用有效地产生伽马射线，我们的模型要求相当极端的喷流功率。
[Abstract]:Blazars is a special class of active galactic nuclei (AGNs), whose radiation is believed to originate in relativistic jets with small angles to our line of sight. They usually show fast light, high polarization, and strong non thermal radiation.Blazars spectral energy distribution (SEDs) usually composed of two wider components: one is low The energy component, from radio to X ray, is the high energy component from X to gamma ray. It is generally believed that the low energy components of their SEDs are produced by the synchrotron radiation of relativistic electrons. However, the origin of the high-energy components is still controversial. The two model is used to explain the high energy components of blazarsSEDs: lepton model and hadron. The lepton model considers that the high energy radiation of blazars is produced by the inverse Compton scattering process of the electron and background photons. The hadron model considers that the high energy radiation of blazars originates from the proton synchrotron radiation or the photon hadron interaction. We studied the blazars high-energy gamma radiation from two sides of the lepton model and the hadron model. The source, the main result is:
1. we studied the location of 21 gamma ray radiant regions with quasi synchronous SEDs. We proposed a method to limit gamma ray radiation. If the gamma ray radiation area is within the wide line area, the inverse Compton (IC) scattering occurs in the KN region, and the gamma ray spectrum should be steeper than the optical near infrared spectrum. The Kogama ray radiation area is outside the wide line area, IC scattering occurs in the Thomson region, the spectral exponent of the gamma ray spectrum should be the same as the spectral exponent of the optical near infrared spectrum. In order to test our theory, we use a region of lepton model including synchronous self Compton (SSC model) and the outer Compton model (EC model) to fit 21 FSRQs quasi synchronization. SEDs, we think that the X ray radiation is from the SSC process, the GeV radiation comes from the EC process, in which the EC radiation may originate from the radiation of the relativistic electronic IC scattering accretion disk and BLR or the radiation of the dust ring. We conjecture that the GeV radiation area of the 5 FSRQs is within the wide line area according to the fitting results of spectral and SEDs, and the other 16 are outside the wide line area. The SEDs fit shows that the energy density of magnetic field and electric field is nearly equal in 21 FSRQs jets.
2. we studied the X ray and gamma ray eruptions of Mrk421 during the June 68, 2008 with an electron accelerated SSC model. The observation found that X rays were obviously related to gamma rays, but the optical and X ray bands were not obviously related. We think that the radiation of Mrk421 may originate from two different components. One is in the external region. The stable component of the domain, which mainly produces optical radiation, is accelerated by the first order Fermi acceleration process in this region. We use the steady-state electron spectrum to produce the SSC radiation in this region. The other is the variation in the internal region, in which the electrons are accelerated by the random acceleration process, and we use a time-dependent SSC model to produce this Radiation in a region. We think that the eruption is caused by the hardening of the electron spectrum by the random acceleration process. The hardening of the electron spectrum will cause the hardening of the X ray and the gamma ray spectrum. In addition, we find that the energy density of the magnetic field and the electron in the two regions are nearly equal.
3. a very hard gamma ray spectrum from remote blazars challenges the standard SSC model. The hard gamma ray spectrum may indicate a spectral composition higher than SSC radiation. We studied the possible origin of the very hard gamma ray spectrum of 1ES1101232. The observation of the possible origin of the.H.E.S.S. showed that there was no obvious light in VHE flow at any time. So we think that the blazar1ES1101232 hard gamma ray spectrum may originate from the radiation of high energy protons. We have proposed a model to explain the blazar1ES1101232 hard gamma ray spectrum. In this model, the radiation of optical and X rays comes from the synchrotron radiation of the original and secondary electrons, and the GeV radiation is produced by the SSC process. The very hard gamma ray originates from the decay of neutral PI 0, in which the neutral PI 0 is produced by the interaction of high energy protons and synchrotron photon P gamma interaction in the jet. Our model can well explain the multiband energy spectrum of 1ES1101232, especially the very hard gamma ray spectrum of 1ES1101232. In order to produce the P gamma interaction effectively Gamma ray, our model requires quite extreme jet power.

【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】：2014
【分类号】：P157.6;P172.3

【参考文献】