LBA observations for project V600 semester 2020OCTS

We have conducted the most comprehensive survey of spectral variability at megahertz frequencies and identified a population of extragalactic sources which show significant variability on year long timescales. We identify two main categories of spectral variability: a uniform increase or decrease across the observed bandwidth and a change in spectral shape. These different categories of spectral variability may be due to different physical mechanisms. However, resolving this detection of spectral variability with current models of source evolution or interstellar scintillation is not possible without high resolution imaging of their morphologies.

本研究开展了迄今最全面的兆赫兹频段（megahertz frequencies）光谱变异性（spectral variability）巡天观测，识别出一批在年际时间尺度上呈现显著光谱变化的河外源（extragalactic sources）。我们将此类光谱变异性划分为两大主要类别：一类为观测带宽内光谱强度呈均匀增减，另一类为光谱形状发生改变。上述不同类别的光谱变异性可能源自不同的物理机制。然而，若缺乏对这些源的形态进行高分辨率成像，我们便无法借助当前的源演化模型或星际闪烁（interstellar scintillation）模型来阐释此次观测到的光谱变异性现象。