AT seminar on 14.7.2017 by Luigi Costamante
Blazars --jetted AGN pointing close to the line of sight-- are the most luminous persistent sources of gamma-rays in the Universe. They seem powered by accretion and extraction of the spin energy of supermassive black holes, and are considered potential sources of UHECR and neutrinos. Despite decades of observations, however, the origin of their gamma-ray emission is still elusive. I will present and discuss recent results from Fermi-LAT, NuSTAR and VHE observations which challenge the standard scenario of their emission, at the two ends of the blazar sequence: in broad-lined quasars and hard-TeV BL Lacs.