Speaker
Description
Active Galactic Nuclei (AGNs) and Gamma-ray Bursts (GRBs) are characterised by highly relativistic outflows. In the first part of the talk, I will discuss how the production of axion-like particles (ALPs) close to the central engine can, on the one hand, either power or disrupt the outflow, and on the other hand, can lead to various observational signatures involving either changes in the prompt photon flux from the source or time delay in the arrival of secondary photons, depending on the coupling of the ALP with Standard Model particles. The non-observation of reprocessed cascade emissions from AGNs and GRBs is usually translated to a limit on the intergalactic magnetic field (IGMF) if plasma instabilities do not play a significant role. In the second part of the talk, I will show how, in addition, ALP processes occurring in AGNs and GRBs can thus be used to modify and refine the IGMF limits.
