Changes in the radio structure of SS 433

Aperture synthesis observations of SS 433 with the VLA at 4.9 and 15 GHz on two different epochs, spaced to show nearly maximum structural changes according to the ephemeris of Margon et al. (1980) are reported. Changes were clearly seen in the structure of the jets. Comparison of the radio maps with the helical pattern expected from twin precessing jets shows some evidence for a helical pattern, although this evidence from the data alone is inconclusive. Linear polarization is clearly associated with the jets and is variable in structure. The degree of polarization is greater than approximately 10% in at least some parts of the radio source, indicative of a highly ordered magnetic field.