2025ApJS..277...50K

We present multifrequency and high-resolution studies of a sample of 24 radio transient sources discovered by comparing the NRAO VLA Sky Survey and the Very Large Array Sky Survey. All of them are characterized by a significant increase in radio flux density over the past two decades. Their convex spectra, small sizes, and high brightness temperatures are typical for young GHz-peaked spectrum (GPS) radio sources and indicative of an active galactic nucleus (AGN) buried in the host galaxy. On the other hand, they are much weaker than the archetypal GPS objects, and their parsec-scale radio structures, although indicating the presence of young radio jets, are similar to radio-quiet AGNs like Seyfert and low-ionization nuclear emission-line region galaxies. Based on the distribution of these objects in power-size (P-D) and peak frequency-size (ν_p-D) diagrams, we suggest that, after stabilizing their radio activity, some of the GHz-peaked radio transients (galaxies and quasars) will develop into radio-intermediate and radio-quiet quasars and low-frequency peaked-spectrum objects. We discuss several possible origins for the transient radio emission in our sources and conclude that changes in the accretion rate combined with low-power radio ejecta are the most probable cause. This is the scenario we also propose for one of our sources, 101841-13, which was independently identified as a candidate tidal disruption event (TDE) based on its infrared variability. However, we cannot exclude that 101841-13 or other sources in our sample are TDEs.