活动星系核（AGN）是位于星系中心的一个致密区域，拥有活动星系核的星系被称为“活动星系”， 活动星系与正常星系相比有很强的射电，红外和X射线辐射，其中X射线辐射基本来自吸积盘，红外辐射来自于尘埃环，射电辐射一般来自喷流的同步辐射。如果视线方向与喷流的方向很接近，核区就容易被观测到，活动星系核就呈现出类星体的特征，在光学，紫外和X射线波段有很强的辐射，这些辐射基本来自于吸积盘的吸积过程。耀变体是特殊的活动星系核，它的相对论喷流几乎指向观测者，其辐射基本来自于喷流中的同步辐射和逆康普顿散射。耀变体辐射有明显的光变，耀变体光变的起源目前尚不明确，是当前研究的热点。一些活动星系核的光变存在周期性，对其周期性的分析可以进一步了解活动星系核中心黑洞，吸积盘和喷流的物理性质。该工作使用不同于传统的类傅里叶方法的随机过程方法celerite分析耀变体4C 01.02的gamma射线和射电波段的长期光变特征，这种方法可以得到更加可靠的功率谱以及减少噪声的影响。结果表明celerite中最简单的阻尼随机游走模型（damped random walk，DRW）可以成功地拟合射电和gamma射线的长期光变曲线，而较为复杂的二阶随机过程（stochastically-driven, damped harmonic oscillator，SHO）并没有显著提升拟合优度。得到的内禀的gamma射线光变特征时标约为3年，如此长的时标不能在轻子辐射模型中产生，但是在强子模型中是允许产生的，我们由此推测4C 01.02长期的gamma射线辐射可能起源于强子过程。射电光变的内禀特征时标约为10年，它可能对应于射电辐射区的逃逸时标，表明射电辐射产生于大尺度喷流。从喷流辐射中得到的特征时标也可能与标准吸积盘联系在一起，其特征时标和典型的吸积盘热时标接近。工作中也用上述方法对活动星系核的周期性光变进行了分析和讨论，列举了其可能的物理起源。
其他摘要
An active galactic nucleus (AGN) is a compact region at the center of a galaxy, galaxies with AGNs are called "active galaxies". Compared with normal galaxies active galaxies have very strong radiation in radio, infrared and X-ray band. If the direction of the line of sight is very close to the direction of the jet, the nuclear region is easy to be observed, and the active galactic nuclei show the characteristics of quasars, which have strong radiation in optical, UV and X-ray bands, this radiation basically comes from the accretion process of the accretion disk. Blazar is a special kind of active galactic nucleus, its relativistic jet almost points to the observer, and its radiation basically comes from synchrotron radiation and inverse Compton scattering in the jet.The radiation of blazar has significant variability.The origin of blazar variability is unclear, which is the hot issue of current research.Here, we use the stochastic process method celerite, which is different from the traditional Fourier-like methods, to analyze the gamma ray and radio long-term variabilities of 4C 01.02. This method can obtain more reliable power spectrum and reduce the influence of noiseThe results show that the simplest kernel in celerite, damped random walk (DRW),can successfully fit both radio and gamma-ray long-term light curves, and the more complex second-order stochastic process (stochastically-driven damped harmonic oscillator，SHO) does not significantly improve the goodness of fit.The intrinsic characteristic timescale of gamma ray variability is about 3 years, and such a long timescale cannot be generated in the leptonic emission model, but it is allowed in the hadronic model. We therefore speculate that the long-term gamma-ray emission of 4C 01.02 may originate from hadronic process.The intrinsic characteristic timescale of radio variability is about 10 years. It may correspond to the escape timescale of the radio emission region, indicating that radio emission is produced in the large-scale jet.The characteristic time scale obtained from jet radiation may also be associated with the standard accretion disk. The characteristic time scale obtained from gamma-ray data is close to the typical thermal time scale of accretion disk.The periodic light variability of AGN is also analyzed by the method used above and discussed, and its possible physical origin is listed.
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