Multi-frequency VLBA observations of compact sources from the Peacock and Wall catalogue

VLBA observations are presented for 6 compact radio sources selected from the Peacock & Wall catalogue. From the new morphological and spectral information, 2 objects that in the Peacock and Wall catalogue are flat spectrum (α ≤ 0.5) sources, appear to be double sided objects with linear sizes of the order of one kpc. Three are core-jet sources and the last one is still an "enigmatic" object. These data complete the sample of small double compact sources in the Peacock & Wall catalogue and the complete list is given. 0.5, many of which are missed in the 3CRR catalogue. A large number of them are genuine flat spectrum sources showing flux density variability and core-jet radio structure on scales from tens of pc to kpc 1 and beyond. In a number of cases, instead, the spectrum is flat at ≈2 GHz, inverted at lower frequencies and steepens at higher frequencies, while the radio structure is on sub-kpc scales. These sources, called GHz Peaked-Spectrum (GPS) sources, are under-represented in low frequency selected samples and their difference from the "truly flat spectrum com- pact sources" was emphasized by the extensors of the catalogue themselves (Peacock & Wall 1982).