Determine the physical origin of delayed gamma-ray–radio flares

Determine whether the multi-year delays between gamma-ray and radio flares in neutrino-blazar candidates arise from opacity effects near the jet base or from the flare originating in a distinct region of the jet.

Background

The paper discusses delayed radio flares observed after gamma-ray activity in sources including TXS 0506+056 and PKS 1424+240. Several physical explanations are possible, including the evolution of synchrotron self-absorption in an expanding emitting region or particle acceleration occurring farther downstream in the parsec-scale jet.

The model developed in the paper favors a scenario in which material associated with the initial inner-jet flare propagates outward and interacts with parsec-scale electron clouds. However, the broader question of whether delayed flares are generally caused by opacity near the jet base or by emission from a physically distinct region remains unresolved.

References

However, whether these delays arise from opacity effects near the jet base, or from the flare originating in a distinct region altogether, remains unresolved.

— An Evolving Leptonic Jet Model for Delayed Radio Flares in Neutrino Blazars  (2608.12696 - Kochocki et al., 13 Aug 2026) in Section 1, subsection “Flaring activity in neutrino blazar candidates”