THE CENTI-ARCSECOND STRUCTURE OF 16 LOW-FREQUENCY VARIABLE SOURCES AT92 CM

We present results of global Mark 2 VLBI snapshot observations at 92 c m of 16 low frequency variable sources. The sample contains 2 radio ga laxies, 9 quasars, 4 BL Lac objects, and 1 source with an uncertain id entification. The sources were selected from a five-year flux monitori ng program using the 305-m radio telescope of the Arecibo Observatory and the 91-m radio telescope of the NRAO (Green Bank) at 1400, 880, 60 6, 430, and 318 MHz. A comparison of our results with VLBI maps at hig her frequencies and WSRT, VLA and MERLIN maps provides constraints on models of the structures of these sources. Our data show clear evidenc e that all sources are resolved at baselines longer than 2 - 6 M lambd a. The results will enable us to look for possible correlations betwee n flux density variability and source structure, aiming to distinguish between intrinsic variability of extragalactic radio sources and vari ability due to propagation phenomena. Finally, we identify a few parti cularly interesting sources for further investigation with higher dyna mical range and at various frequencies.