The variability of the Crab Nebula in radio: No radio counterpart to gamma-ray flares

Abstract

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.

Accepted to MNRAS; 13 pages, 6 figures

References in corpus (7)

• Gamma-ray flares from the Crab Nebula
• Discovery of Powerful Gamma-Ray Flares from the Crab Nebula
• Pulsar Wind Nebulae as Cosmic Pevatrons: A Current Sheet's Tale
• Spitzer Space Telescope Infrared Imaging and Spectroscopy of the Crab Nebula
• Far-infrared and sub-mm observations of the Crab nebula
• Optical and infrared observations of the Crab Pulsar and its nearby knot
• Imaging algorithms in radio interferometry

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• Wide-Band Spectra of Giant Radio Pulses from the Crab Pulsar
• The Crab Nebula at subarcsecond resolution with the International LOFAR Telescope