VLBI studies of radio-quiet AGN : origin of radio emission and tracing its connection with changing-look events

While radio emission from radio-loud AGN is dominated by relativistic jets, different competing mechanisms for radio emission exist for radio-quiet AGN. A fraction of these RQ AGN have undergone violent changing-look events in the recent past, which make them ideal testbeds to test for evolution in and origin of radio emission at the most compact VLBI (<pc) scales. We present recent results obtained from the VLBI monitoring of the changing look AGN 1ES 1927+654 and Mrk 590. We find that the origin of the radio core (<pc) emission for 1ES can be possibly attributed to synchrotron emission by non-thermal electrons from the corona, which is generally responsible for X-ray emission by thermal electrons, thereby hinting at a possibility of a hybrid corona. In Mrk 590, in addition to the core, we find extended anisotropic radio emission with VLBI observations and trace its evolution over 7 years to find possible connection with a changing-look event in its past. Our study paves the way for future multi-wavelength follow-ups of changing-look sources to constrain open questions related to radio emission from radio-quiet AGN, nature of the corona and jet launching.