Blazars are galaxies whose central,supermassive black holes are accreting material from surrounding regions. Although black gap accretion happens in many galaxies and situations, in the case of a blazar the infalling material erupts into a powerful, and narrow beam of tall velocity charged particles that,fortuitously, is pointed in our direction. The charged particles produce gamma ray photons, or each photon packing over a hundred million times the energy of the highest energy X-ray photon seen by the Chandra X-ray Observatory. The electron beam produces many other effects,and in blazars these include rapid, strong, or incessant variability. They sometimes also include the ability to generate tall-energy gamma rays.
Source: phys.org