The blazar paradigm and its discontents
arXiv:1408.6453
Abstract
The standard blazar paradigm consists of a supermassive black hole that expels relativistic jets of magnetized plasma in our direction. This plasma entrains nonthermal synchrotron-emitting electrons that furthermore scatter internally-produced synchrotron photons as well as externally-produced photons from the accretion-disk, the broad-line region, and the infrared-emitting torus. This picture has been very successful in reproducing the two-humped blazar spectral energy distribution. Yet various discontents persist, including (1) ultra-short variability at TeV energies that is much shorter than the black hole's dynamical timescale; (2) very-high energy (VHE; >100 GeV) radiation from FSRQs; (3) evidence for a hard spectral component in high-synchrotron peaked objects, found when deabsorbing the measured VHE spectrum using conventional extragalactic background light (EBL) models; (4) an unusual slowly varying class of BL Lac objects; (5) location of the gamma-ray emission region. Some of these problems can be resolved by introducing a hadronic component into the blazar paradigm, consistent with the hypothesis that blazars are sources of ultra-high energy cosmic rays. Gamma-ray observations with the Cherenkov Telescope Array and neutrino observations with IceCube will be important to test this hypothesis.
12 pages, 5 figures, proceedings for "High Energy Astrophysics in Southern Africa," Bloemfontein, New Free State, South Africa, 23-25 April, 2014; added references and text edits
References in corpus (4)
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