Related papers: Active Galaxies as Particle Accelerators
Understanding the acceleration of Ultra High Energy Cosmic Rays is one of the great challenges of contemporary astrophysics. In this short review, we summarize the general observational constraints on their composition, spectrum and…
Active Galactic Nuclei (AGN) may emit highly collimated and intense jets of relativistic electrons which upscatter ambient photons. These electrons can also scatter off the cold dark matter halo of the galaxy to produce high energy photons…
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10^12 electron Volts (eV) and are…
The presence of relativistic particles at the center of our galaxy is evidenced by the diffuse TeV emission detected from the inner $\sim$$2^\circ$ of the Galaxy. Although it is not yet entirely clear whether the origin of the TeV photons…
The highest energy cosmic rays could be produced by drifts in magnetized, cylindrically collimated, sheared jets of powerful active galaxies (i.e. FR II radiogalaxies; radio loud quasars and high power BL Lacs). We show that in such…
Supermassive black holes are believed to be the central power house of active galactic nuclei. Applying the pulsar outer-magnetospheric particle accelerator theory to black-hole magnetospheres, we demonstrate that an electric field is…
The launch of the Fermi gamma-ray space telescope and the imaging air Cerenkov telescopes H.E.S.S., MAGIC, and VERITAS have substantially transformed our knowledge of gamma-ray sources in the last decade. The extragalactic gamma-ray sky is…
Nature produces cosmic ray particles, probably protons, with energies well above $10^{20}$ eV -- how are they produced? Where do they come from? Gamma rays with energies above $10^{13}$ eV are produced in jets of active galaxies -- are…
Massive black holes in active galaxies are immersed in huge concentrations of late type stars in the galactic bulges and also early type massive stars in the nuclear stellar clusters which are additionally surrounded by quasi-spherical…
We perform Monte Carlo simulations of transrelativistic shear acceleration dedicated to a jet-cocoon system of active galactic nuclei. A certain fraction of galactic cosmic rays in a halo is entrained, and sufficiently high-energy particles…
Accelerated particles are ubiquitous in the Cosmos and play a fundamental role in many processes governing the evolution of the Universe at all scales, from the sub-AU ones relevant for the formation and evolution of stars and planets to…
We discuss the possibility that accreting black hole systems can be sources for dark matter flux through several different mechanisms. We firstly discuss two types of systems: coronal thermal plasmas around supermassive black holes in…
Context: The most nearby active galaxy Cen A has attracted considerable attention as a detected TeV gamma-ray and possible ultra-high energy (UHE) cosmic-ray emitter. Aims: We investigate the efficiency of particle acceleration close to the…
Supermassive black holes in the centers of galaxies are very common. They are known to rotate, accrete, spin down and eject highly relativistic jets; those jets pointed at us all seem to show a spectrum with two strong bumps, one in the TeV…
Evidence for high-energy astrophysical PeV neutrinos has been found in the IceCube experiment from an analysis with a 7.5 year (2010 - 2017) data. Active galactic nuclei (AGN) are among the most prominent objects in the universe, and are…
The origin of ultra high energy cosmic rays promises to lead us to a deeper understanding of the structure of matter. This is possible through the study of particle collisions at center-of-mass energies in interactions far larger than…
Laboratory experiments to explore plasma conditions and stimulated particle acceleration can illuminate aspects of the cosmic particle acceleration process. Here we discuss the cosmic-ray candidate source object variety, and what has been…
We discuss theoretical issues and experimental data that brought the ultra high energy cosmic rays in the list of Nature's greatest puzzles. After many years of research we still do not know how astrophysical acceleration processes can…
Jets of active galactic nuclei are potential accelerators of ultra high-energy cosmic rays. Supernovae can occur inside these jets and contribute to cosmic ray acceleration, particularly of heavy nuclei, but that contribution has been…
Cosmic ray interactions that produce high-energy neutrinos also inevitably generate high-energy gamma rays, which finally contribute to the diffuse high-energy gamma-ray background after they escape the sources. It was recently found that,…