HIGH-FREQUENCY VLA OBSERVATIONS OF LOW-REDSHIFT QUASARS - CORE STRUCTURE, VARIABILITY AND ORIENTATION

We discuss high-frequency radio maps of 33 low-redshift quasars, taken with the VLA(2) (Very Large Array) in the A-configuration, at 1.3, 2, and 6 cm. In six sources we report the detection of new detailed stru cture. The 6 cm data are second-epoch observations and are used in dis cussion of core variability. Core variability is found to be present i n both lobe- and core-dominated sources, with 12 quasars displaying si gnificant flux changes over the two epochs. The majority of variable s ources have flat or positive spectral indices, in agreement with other recent variability studies. We also consider the core fraction distri bution of our sample of 114 quasars to redshift 2. This quantity does not correlate with source bend-angle or lobe length ratio as might be expected if the core flux is enhanced due to beaming when the source i s aligned close to the line of sight. We confirm the correlation with apparent size, with a few exceptions, and show that these results are consistent with a source evolution scenario discussed in earlier paper s.