Long term variability of gigahertz-peaked spectrum sources and candidates
Long term variability of gigahertz-peaked spectrum sources and candidates
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DOI：
10.1051/0004-6361:20041886
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发表时间：
2005-06
影响因子：
6.5
通讯作者：
I. Torniainen;M. Tornikoski;H. Teräsranta;M. Aller;H. Aller
中科院分区：
文献类型：
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作者：
I. Torniainen;M. Tornikoski;H. Teräsranta;M. Aller;H. Aller
我们结合了新的数据，从我们的观测活动和文献中的数据，以构建无线电连续谱的样本，主要是类星体型高峰值千兆赫兹峰值频谱（GPS）源候选人。我们还研究了所谓的“真正的”GPS源和其他倒频谱源的文献的频谱和变化。对于我们的许多样本源，我们现在有超过二十年的数据，使我们能够研究它们的长期行为。基于我们先前的结果，我们期望找到几个新的高峰值GPS源。相反，我们发现，即使是大多数的“真正的”GPS源停止坚持通用GPS源属性时，使用这些良好的采样长期数据集。在我们从文献中抽取的35个倒频谱源的样本中，只有5个似乎与GPS特性一致，即使在这些源中，也有两个样本太稀疏，无法对它们的变异性做出坚定的结论。13个“真正的”全球定位系统来源表现出明显的活动，这与这些来源预期的低变异性不同。我们的新候选者中没有一个被证明既有凸谱又有很少或没有变异性，但有一个可变源具有一致的凸谱。其余的都有平坦的频谱，但频谱的上包络对于四个极端可变的源来说是明显凸的。类似的连续谱与平坦的下包络和凸的上包络观察到8个先前确定的倒谱源。根据这项研究，真正的类星体类型的GPS源是罕见的，但有大量的高度可变的源，可以有一个凸频谱峰值在高无线电频率（高达约。100 GHz）。许多文献中的GPS源太容易被归类为GPS源的基础上太稀疏的数据，和长期的变化研究是必不可少的识别源一致凸连续谱。
We have combined new data from our observing campaigns and data from the literature to construct the radio continuum spectra for a sample of mostly quasar-type high peaking gigahertz-peaked spectrum (GPS) source candidates. We have also studied the spectra and variability of so called "bona fide" GPS sources and other inverted-spectrum sources from the literature. For many of our sample sources we now have data spanning over two decades, enabling us to study their long term behaviour. Based on our earlier results we expected to find several new high peaking GPS sources. Instead we found out that even most of the "bona fide" GPS sources cease to adhere to the generic GPS source properties when using these well-sampled long term data sets. In our sample of 35 inverted-spectrum sources from the literature only five seem to be consistent with the GPS properties, and even out of these sources two are too sparsely sampled to firmly make conclusions about their variability. Thirteen of the "bona fide" GPS sources exhibit pronounced activity, which diverges from the low variability expected from these sources. None of our new candidates turned out to have both a convex spectrum and little to no variability, but there is one variable source with a consistently convex spectrum. All the rest have flat spectra, but the upper envelope of the spectrum is clearly convex for four extremely variable sources. Similar continuum spectra with a flat lower envelope and a convex upper envelope are observed for eight previously identified inverted-spectrum sources. According to this study the genuine quasar-type GPS sources are rare but there is a large number of highly variable sources that can have a convex spectrum peaking at high radio frequencies (up to ca. 100 GHz) during flares. Many of the GPS sources from the literature have too easily been classified as GPS sources based on too sparse data, and studying the long term variability is essential for identifying the sources with consistently convex continuum spectra.