CTD 135的高变$γ$射线发射及其紧凑对称结构的意义
Highly Variable $γ$-Ray Emission of CTD 135 and Implications for its Compact Symmetric Structure
摘要：
利用$\sim$ 11年的Fermi/LAT观测资料，研究了典型致密对称天体CTD 135的$γ$射线发射特性.我们发现它有明亮的和显著变化的GeV发射，与$L_γ\sim10^{47}$ erg的$^{-1}$和TS $_{\rm var}=1002$的变化指数的$γ$射线光度。在全球95%的虚警水平上探测到一个周期为$\sim$ 460天的准周期振荡（QPO）。这些$γ$射线发射特征与耀变体相似。它的宽带谱能量分布（SED）可以归因于在核心区和扩展区加速的相对论电子的辐射。模拟结果表明，$γ$射线来自核心区，其多普勒增强因子为$δ\sim10.8$，并以小视角相对论运动，类似于耀变体喷流。根据分析结果，我们认为CTD 135中心发动机的幕式活动导致了类似耀变体的喷流和类似银河系费米泡的泡状叶瓣。强的$γ$射线辐射和明显的变化是来自喷流辐射和对称的射电结构归因于气泡。CTD 135的喷流辐射功率和以爱丁顿光度为单位的盘光度遵循与其他年轻射电星系相同的关系，表明其喷流辐射也可能由爱丁顿比驱动。
英文摘要：
The $γ$-ray emission properties of CTD 135, a typical compact symmetric object (CSO), are investigated with $\sim$11-year Fermi/LAT observations. We show that it has bright and significantly variable GeV emission, with the $γ$-ray luminosity of $L_γ\sim10^{47}$ erg s$^{-1}$ and a variation index of TS$_{\rm var}=1002$. A quasi-periodic oscillation (QPO) with a periodicity of $\sim$460 days is detected in the global 95\% false-alarm level. These $γ$-ray emission features are similar to that of blazars. Its broadband spectral energy distribution (SED) can be attributed to the radiations of the relativistic electrons accelerated in the core region and the extended region. The SED modeling shows that the $γ$-rays are from the core region, which has a Doppler boosting factor of $δ\sim10.8$ and relativistically moves with a small viewing angle, being similar to blazar jets. On the base of the analysis results, we propose that the episodic activity of the central engine in CTD 135 results in a blazar-like jet and the bubble-like lobes as the Fermi bubbles in the Galaxy. The strong $γ$-ray emission with obvious variability is from the jet radiations and the symmetric radio structure is attributed to the bubbles. The jet radiation power and disk luminosity in units of Eddington luminosity of CTD 135 follow the same relation as other young radio galaxies, indicating that its jet radiation may be also driven by the Eddington ratio.
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