Conclusions

55 sources used for calibration purposes by the MOST at a frequency of 843 MHz have been observed irregularly over a 13 year interval. We have developed an algorithm to process these data and produce a light curve for each source. Our analysis shows that 18 of these sources can be considered variable. There is some suggestion that these sources are distributed at lower Galactic latitudes than the 19 sources whose flux densities are unvarying. This suggests that variability at 843 MHz on time scales of 1-10 years is predominantly due to scintillation in the Galactic ISM rather than effects intrinsic to the source. A possible correlation between modulation index and spectral index can be explained qualitatively in terms of a variation in the core fraction with orientation of the radio axis to the line of sight.

© Copyright Astronomical Society of Australia 1997