Shao et al. present multifrequency radio data for a sample of Narrow-Line type 1 Seyfert (NLS1) galaxies, studying the long-term radio variability of five sources and comparing it to their gamma-ray state. They find that the gamma-ray emitting NLS1 galaxies are highly variable radio emitters and that there are several instances of contemporaneous flaring activity between the radio and gamma-ray bands, but also cases of significant radio outbursts without associated gamma-ray activity.

The light curves above show the radio (top) and gamma-ray (bottom) variability of PMN J0948+0022, the first NLS1 to be detected by NASA’s Fermi gamma-ray satellite. The gamma-ray light curve shows pronounced activity during the first ∼8 years of the mission, and lower level activity until early 2020, but relative quiescence thereafter.  There is a pronounced radio flare starting in late 2020, which shows the “classical” radio flare characteristics of peaking earlier and higher at higher frequencies, with some evidence for a small secondary peak in early 2023. This radio flare however is not accompanied by any significant gamma-ray activity, indicating differences in the location and/or environment where the outbursts occurred.