|On the Nature of High Frequency Peakers: Young Radio Sources or Flaring Blazars?
|386, Extragalactic Jets: Theory and Observation from Radio to Gamma Ray
|Orienti, M.; Dallacasa, D.
|High Frequency Peaker (HFP) radio sources are an extreme class of active galactic nuclei whose nature has not been fully understood yet. They are compact objects with a simple convex radio spectrum which turns over at frequencies well above a few GHz. In the context of evolutionary models such sources are likely to represent the earliest stage in the individual radio source evolution, with typical ages of a few hundred years. The selection tools used to identify a source as an HFP, the convex shape of the radio spectrum and the high turnover frequency, can introduce a contamination by beamed objects, like blazars, which can occasionally show a convex spectrum during particular phases of their variability.
We present the results of new multi-epoch, multi-frequency VLA observations of the 55 sources from the Bright HFP sample. The comparison between such results and the pc-scale morphology information already acquired enables us to determine the nature of HFP radio sources.