6 Conclusions

We have conducted a program of multi-wavelength VLA observations of the suspected low frequency variable sources 0235-197 and 1203+043. Since 0235-197 is not polarized at 320MHz, its variability cannot be accounted for by instrumental polarization effects as in the case of 3C 159. 0235-197 may contain a low frequency component sufficiently compact and bright as required by the refractive scintillation model for low frequency variability. Our observations have insufficient resolution to test this suggestion; low frequency VLBI observations are required for this purpose. However, this component would have to have extremely unusual properties among hot spots in radio sources.

In our high frequency images of 1203+043 we have identified the core of the radio source; its location indicates that the source has a large apparent asymmetry. At 320MHz, this source shows no polarization. However, it does have an additional, steep-spectrum component at this frequency; this previously-undetected component lies perpendicular to the main axis and predominantly to one side. However, the overall morphology of 1203+043 at low frequencies seems similar to that of the "X''-shaped sources like NGC 326. From its morphology and component sizes, we conclude that 1203+043 is likely not variable at low frequencies and that its inclusion in such catalogs is spurious.

Acknowledgements

The authors like to thank the referee, Dr. Steve Spangler for his comments to the paper and Dr. Ian Browne for a critical reading of the manuscript. FM thanks Miller Goss, Assistant Director, NRAO, Socorro, for his hospitality during period when part of the work was done. The National Radio Astronomy Observatory is operated by Associated Universities Inc., under cooperative agreement with the National Science Foundation; AIPS is NRAO's Astronomical Image Processing System.