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Published August 11, 2006 | Published
Journal Article Open

15-GHz variability of 9C sources


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.

Additional Information

© 2006 The Authors. Journal compilation © 2006 RAS. Accepted 2006 May 17. Received 2006 April 20; in original form 2005 September 29. We thank the referee, Merja Tornikoski, for helpful comments. This work has made use of the NED, which is operated by the JPL, California Institute of Technology, under contract with the National Aeronautics and Space Administration. The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

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