Characterisation of Long Baseline Calibrators at 2.3 GHz
  We present a detailed multi-epoch analysis of 31 potential southern
hemisphere radio calibrators that were originally observed as part of a program
to maintain the International Celestial Reference Frame (ICRF). At radio
wavelengths, the primary calibrators are Active Galactic Nuclei (AGN), powerful
radio emitters which exist at the centre of most galaxies. These are known to
vary at all wavelengths at which they have been observed. By determining the
amount of radio source structure and variability of these AGN, we determine
their suitability as phase calibrators for long baseline radio interferometry
at 2.3 GHz. For this purpose, we have used a set of complementary metrics to
classify these 31 southern sources into five categories pertaining to their
suitability as VLBI calibrators. We find that all of the sources in our sample
would be good interferometric calibrators and almost ninety per cent would be
very good calibrators.
