Abstract
Black holes (BHs) play major roles in astrophysical processes through phenomena like accretion and relativistic jets, acting as cosmic ray accelerators and gamma-ray emitters. They encompass stellar-mass BHs in binaries and supermassive BHs in active galactic nuclei (AGNs), being also crucial for powering gamma-ray bursts (GRBs). Relativistic jets from BHs attain high Lorentz factors, ess…