Making Sense of Neutrino-Bright Blazars

The radio and gamma-ray bright jets of blazars have historically been considered as favorable sites for high-energy particle acceleration and neutrino production. Accelerated hadronic populations are assumed necessary, while external fields or radiation within the jet may provide targets. After nearly fifteen years of observation from the IceCube South Pole Neutrino Observatory, only a small handful of individual blazars show substantial excesses, and more sensitive probes of the stacked population set constraining limits. The few potential neutrino blazars – TXS 0506+056, PKS 1424+240 and GB6 J1542+6129 – show similar spectral energy distributions and flaring activity. We consider how such radio and gamma-ray activity may relate to the location of neutrino production. Given this model, we further test whether the wider population of blazars simply offers an inefficient neutrino production environment, or if the proton luminosities of the few known neutrino-bright blazars are actually exceptional.