SIMBAD references

We present results of global Mark 2 VLBI snapshot observations at 92cm of 16 low frequency variable sources. The sample contains 2 radio galaxies, 9 quasars, 4 BL Lac objects, and 1 source with an uncertain identification. The sources were selected from a five-year flux monitoring 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, 606, 430, and 318MHz. A comparison of our results with VLBI maps at higher frequencies and WSRT, VLA and MERLIN maps provides constraints on models of the structures of these sources. Our data show clear evidence that all sources are resolved at baselines longer than 2-6 Mλ. The results will enable us to look for possible correlations between flux density variability and source structure, aiming to distinguish between intrinsic variability of extragalactic radio sources and variability due to propagation phenomena. Finally, we identify a few particularly interesting sources for further investigation with higher dynamical range and at various frequencies.