标题： 银河平面可变无线电波源的结构和光谱特性 显示英文标题

标题： Structural and spectral properties of Galactic plane variable radio sources

摘要： 在时间域内，尤其是在银河系平面方向上，由于与恒星、恒星以及超大质量黑洞相关的各种高能活动，射电天空可能表现出显著的变化。利用美国甚大阵列（VLA）对银河系平面在5.0 GHz的多期观测数据，Becker等人（2010年）给出了一个包含39个变源的目录，其流量密度范围在1到70毫焦耳之间。 为了探测这些源的射电结构和光谱，我们使用甚长基线干涉成像技术观测了其中的17个源，并从文献中收集了额外的多频数据。我们用Westerbork综合射电望远镜在5 GHz处检测到了所有这些源，但只有G23.6644-0.0372源可以用欧洲甚长基线干涉网络（EVN）观测到。结合其十年尺度的变化和多频射电光谱，我们认为它是一个大小约为<~10 pc的河外峰谱源。其余源被EVN的长基线所解析，这要么是因为银河纬度<1度时强烈的散射扩展效应，要么是因为它们本质上具有角秒尺度上的非常扩展的结构。 根据它们的光谱和结构特性，我们发现样本具有多样性。我们注意到两个年轻的H II区，并发现了一个射电星和一个候选行星状星云。其余的源很可能与射电活动星系核（AGN）有关。其中两个还显示出角秒尺度的微弱喷流活动。样本研究表明，即使是银河系平面中的变化射电源，AGN也是常见的。 显示英文摘要

摘要： In the time domain, the radio sky in particular along the Galactic plane direction may vary significantly because of various energetic activities associated with stars, stellar and supermassive black holes. Using multi-epoch Very Large Array surveys of the Galactic plane at 5.0 GHz, Becker et al. (2010) presented a catalogue of 39 variable radio sources in the flux density range 1-70 mJy. To probe their radio structures and spectra, we observed 17 sources with the very-long-baseline interferometric (VLBI) imaging technique and collected additional multi-frequency data from the literature. We detected all of the sources at 5 GHz with the Westerbork Synthesis Radio Telescope, but only G23.6644-0.0372 with the European VLBI Network (EVN). Together with its decadal variability and multi-frequency radio spectrum, we interpret it as an extragalactic peaked-spectrum source with a size of <~10 pc. The remaining sources were resolved out by the long baselines of the EVN because of either strong scatter broadening at the Galactic latitude <1 deg or intrinsically very extended structures on centi-arcsec scales. According to their spectral and structural properties, we find that the sample has a diverse nature. We notice two young H II regions and spot a radio star and a candidate planetary nebula. The rest of the sources are very likely associated with radio active galactic nuclei (AGN). Two of them also displays arcsec-scale faint jet activity. The sample study indicates that AGN are commonplace even among variable radio sources in the Galactic plane.