Caltech-NRAO Stripe 82 Survey（CNSS）论文V：AGNs that transitioned to radio-loud state
Caltech-NRAO Stripe 82 Survey (CNSS) Paper V: AGNs that transitioned to radio-loud state
摘要：
最近的一项为期多年的加州理工学院NRAO条纹82调查（CNSS）揭示了一组在$>$消失5- 20年后作为新射电源出现的物体。它们是相对于20厘米射电天空微弱图像（FIRST）调查的瞬态现象，构成了第一个更新的射电活动的无偏样本。在这里，我们提出的后续行动，无线电，光学和X射线研究他们。这个星系群由12个源组成，包括类星体和具有宽红移（$\rm 0.04 < z < 1.7$）和光度（$\rm 22<log_{10}[L_{1.4GHz}/W~Hz^{-1}]>24.5$）分布的星系。它们在活动的第一阶段的无线电特性，即凸光谱和紧凑的形态，使它们都被归类为千兆赫兹峰值频谱（GPS）源。我们的结论是光谱的变化是新生的射电喷流的演变的结果。我们的观测结果表明，在接下来的几年活动中，GPS星系保持了光谱的凸形，而GPS类星体迅速转变为平谱源，这可能导致它们不能被识别为年轻源。瞬态源的辐射热光度、黑洞质量和喷流功率变化范围很大，表明年轻射电天体群的总体多样性更大。我们还认为，吸积盘光度（吸积率）的微小变化可能足以点燃几十年尺度上演变的低功率射电活动。
英文摘要：
A recent multi-year Caltech-NRAO Stripe 82 Survey (CNSS) revealed a group of objects that appeared as new radio sources after $>$5--20 years of absence. They are transient phenomena with respect to the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey and constitute the first unbiased sample of renewed radio activity. Here we present the follow-up, radio, optical and X-ray study of them. The group consist of 12 sources, both quasars and galaxies with wide redshift ($\rm 0.04 < z < 1.7$) and luminosity ($\rm 22<log_{10}[L_{1.4GHz}/W~Hz^{-1}]>24.5$) distribution. Their radio properties in the first phase of activity, namely the convex spectra and compact morphology, allow them all to be classified as gigahertz-peaked spectrum (GPS) sources. We conclude that the spectral changes are a consequence of the evolution of newly-born radio jets. Our observations show that over the next few years of activity the GPS galaxies keep the convex shape of the spectrum, while GPS quasars rapidly transform into flat-spectrum sources, which may result in them not being recognized as young sources. The wide range of bolometric luminosities, black hole masses and jet powers among the transient sources indicates even greater population diversity in the group of young radio objects. We also suggest that small changes of the accretion disc luminosity (accretion rate) may be sufficient to ignite low-power radio activity that evolves on the scale of decades.
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