DOI

https://doi.org/10.48717/kd6v-rm63

Project

EZ041

Title

e-EVN: EZ041A, ER057C

Abstract

We propose EVN observations of a sample of 22 quasars that have recently undergone dramatic radio brightening, likely marking the onset or re-triggering of radio activity. These sources were undetected in the NVSS (?1993) but emerged as compact radio sources in the first epoch of the VLASS (?2018), exhibiting luminosity increases > 200% and radio spectra peaking at GHz frequencies. Multi-frequency radio data from NVSS, FIRST, VLASS, ASKAP, and LOFAR indicate that these objects belong to the radio-intermediate regime, well below the main evolutionary track of powerful radio-loud AGNs. At their typical redshift (z=1–1.5), simple orientation-driven variability of a strongly beamed core would require unrealistically high intrinsic luminosities, inconsistent with their previous non-detections. EVN observations at 5 and 8 GHz will resolve the sources on parsec scales, enabling identification of compact cores and nascent jet structures. Measurements of brightness temperatures, spectral indices, and source compactness will provide key diagnostics to distinguish simple core variability from the emergence of a new or restarted phase of jet activity. This project targets AGNs in the earliest observable stages of radio evolution, offering a unique opportunity to probe the physical mechanisms responsible for triggering radio emission.