The role of supernovae inside AGN jets in UHECR acceleration

TL;DR

This paper investigates how supernovae occurring inside active galactic nucleus jets can serve as significant sites for accelerating ultra high-energy cosmic rays, especially heavy nuclei, potentially surpassing galactic cosmic ray entrainment.

Contribution

It provides the first detailed analysis of supernova-jet interactions as sources of ultra high-energy cosmic rays, highlighting their energy contribution and acceleration potential.

Findings

Supernova-jet interactions can produce energies exceeding 10 EeV.

Despite low occurrence rates, these interactions may outpace galactic cosmic ray entrainment.

Supernovae inside jets can generate sufficient energy to accelerate heavy nuclei to ultra high energies.

Abstract

Jets of active galactic nuclei are potential accelerators of ultra high-energy cosmic rays. Supernovae can occur inside these jets and contribute to cosmic ray acceleration, particularly of heavy nuclei, but that contribution has been hardly investigated so far. We carried out a first dedicated exploration of the role of supernovae inside extragalactic jets in the production of ultra high-energy cosmic rays. We characterized the energy budget of supernova-jet interactions, and the maximum possible energies of the particles accelerated in those events, likely dominated by heavy nuclei. This allowed us to assess whether these interactions can be potential acceleration sites of ultra high-energy cosmic rays, or at least of their seeds. For that, we estimated the cosmic ray luminosity for different galaxy types, and compared the injection rate of cosmic ray seeds into the jet with that due to galactic cosmic ray entrainment. Since the supernova is fueled for a long time by the luminosity of the jet, the energy of a supernova-jet interaction can be several orders of magnitude greater than that of an isolated supernova. Thus, despite the low rate of supernovae expected to occur in the jet, they could still provide more seeds for accelerating ultra high-energy particles than cosmic ray entrainment from the host galaxy. Moreover, these interactions can create sufficiently efficient accelerators to be a source of cosmic rays with energies $\gtrsim 10$~EeV. Supernova-jet interactions can contribute significantly to the production of ultra high-energy cosmic rays, either directly by accelerating these particles themselves or indirectly by providing pre-accelerated seeds.