蟹状星云在射电中的变化：没有射电对应于gamma-ray耀斑
The variability of the Crab Nebula in radio: No radio counterpart to gamma-ray flares
摘要：
我们提出了新的Jansky甚大阵（VLA）的蟹状星云在5.5 GHz的无线电图像，在两个时代相隔6天约两个月后，在2012年7月的伽马射线耀斑。我们发现，无论是在我们目前的观测之间的6天间隔内，还是在目前的观测与2001年的观测之间，蟹状星云的射电辐射都没有明显的变化。任何射电耀斑的对应物的射电光度都是星云的<~ $2 \times 10^{-4}$倍。然而，将我们的图像与2001年的图像进行比较，我们确实发现了射电亮度的变化，幅度高达10%，这些变化发生在整个星云的十年时间尺度上。变化的形态复杂，提示有结缔组织和多节结构。变化性更强，时间尺度可能更短，更接近星云的中心。我们进一步发现，即使VLA具有良好的紫外覆盖范围和信噪比，反卷积误差也远大于噪声，在这种特殊情况下，反卷积误差高达星云峰值亮度的1.2%。
英文摘要：
We present new Jansky Very Large Array (VLA) radio images of the Crab Nebula at 5.5 GHz, taken at two epochs separated by 6 days about two months after a gamma-ray flare in 2012 July. We find no significant change in the Crab's radio emission localized to a region of <2 light-months in radius, either over the 6-day interval between our present observations or between the present observations and ones from 2001. Any radio counterpart to the flare has a radio luminosity of <~ $2 \times 10^{-4}$ times that of the nebula. Comparing our images to one from 2001, we do however find changes in radio brightness, up to 10% in amplitude, which occur on decade timescales throughout the nebula. The morphology of the changes is complex suggesting both filamentary and knotty structures. The variability is stronger, and the timescales likely somewhat shorter, nearer the centre of the nebula. We further find that even with the excellent uv~coverage and signal-to-noise of the VLA, deconvolution errors are much larger than the noise, being up to 1.2% of peak brightness of the nebula in this particular case.
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