15-GHz variability of 9C sources |
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| Authors: | R C Bolton C J Chandler G Cotter T J Pearson G G Pooley A C S Readhead J M Riley E M Waldram |
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| Institution: | Cavendish Astrophysics, Department of Physics, J. J. Thomson Avenue, Cambridge CB3 0HE;National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA;Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH;California Institute of Technology, 1201 East California Blvd, Pasadena, CA 91125, USA |
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| Abstract: | We present results from a 3-yr study of the 15-GHz variability of 51 9C sources. 48 of these sources make up a subsample of a larger one complete to 25 mJy in 9C, and as the sources are selected pseudo-randomly the results should be representative of the complete sample. 29 per cent of this subsample are found to be variable above the flux calibration uncertainties of ～6 per cent. 50 per cent of the flat-spectrum objects are variable whilst none of the steep-spectrum objects or the objects with convex spectra peaking below 5 GHz are variable. Nine of the objects studied have convex spectra and peak frequencies above 5 GHz; eight of these were found to vary at 15 GHz, suggesting that the high-frequency peaking class in this sample is largely populated by objects with jets aligned close to the line of sight whose emission is dominated by beamed components. |
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| Keywords: | surveys galaxies: active radio continuum: general |
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