Related papers: ORIGIN OF THE HIGH ENERGY EXTRAGALACTIC DIFFUSE GA…
The origin of high-energy cosmic rays, atomic nuclei that continuously impact Earth's atmosphere, has been a mystery for over a century. Due to deflection in interstellar magnetic fields, cosmic rays from the Milky Way arrive at Earth from…
Dark matter annihilation and other processes may precipitate a flux of diffuse ultra-high energy $\gamma$-rays. These $\gamma$-rays may be observable in present day experiments which observe diffuse fluxes at the GeV scale. Yet the universe…
Gamma ray emission lines resulting from accelerated particle bombardment of ambient gas can serve as an important spectroscopic tool for abundance determinations. The method is illustrated by considering the gamma ray line emission observed…
Clusters of galaxies and the large scale filaments that connect neighboring clusters are expected to be sites of acceleration of charged particles and sources of non-thermal radiation from radio frequencies to gamma rays. Gamma rays are…
The observation of the diffuse Galactic gamma ray flux is the most powerful tool to study cosmic rays in different regions of the Galaxy, because the energy and angular distributions of the photons encode information about the density and…
As of early 2009, latest results on Galactic sources (mainly shell-type and plerionic supernova remnants), as observed in the very-high-energy gamma-ray domain, are reviewed. A particular attention is given to those obtained with the…
Elliptical galaxies are generally luminous sources of X-ray radiation, and contain large amounts of hot, interstellar gas. In the brighter X-ray galaxies, the inferred masses of hot gas are consistent with those expected given the present…
We propose that repeated photoexcitation/ionization of high Z atoms of highly relativistic flows by star light in dense stellar regions followed by emission of decay/recombination photons, which are beamed and boosted to gamma ray energies…
Gamma rays constitute a privileged point of view for the study of the extreme Universe. Unlike charged cosmic rays, which are thought to have a common origin, gamma rays are not deflected by galactic and intergalactic magnetic fields. This…
The origin of the highest-energy cosmic rays remains a mystery. The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions have strongly constrained most models…
The successful discovery of X-ray, optical and radio afterglows of GRB has made possible the identification of host galaxies at cosmological distances. The energy release inferred in these outbursts place them among the most energetic and…
We discuss several effects due to lensing of ultra high energy cosmic rays by the regular component of the galactic magnetic field. Large flux magnification around caustics can be a significant source of clustering in the arrival directions…
Recent observations of cosmic rays (CRs) have revealed a two-component anomaly in the spectra of primary and secondary particles, as well as their ratios, prompting investigation into their common origin. In this study, we incorporate the…
Several of the models for origin of the highest energy cosmic rays also predict significant neutrino fluxes. A common factor of the models is that they must provide sufficient power to supply the observed energy in the extragalactic…
We review recent progress in our understanding of the physics of energetic particles in our Galaxy, in active galaxies such as starburst galaxies, in active galactic nuclei and in the jets and radio hot spots of powerful radio galaxies and…
The Large High-Altitude Air Shower Observatory (LHAASO) recently published measurements of diffuse Galactic gamma-ray emission (DGE) in the 10-1000 TeV energy range. The measured DGE flux is significantly higher than the expectation from…
Recent EGRET observations of the diffuse Galactic gamma-ray emission reveal a spectrum which is incompatible with the assumption that the cosmic ray spectra measured locally hold throughout the Galaxy: the spectrum above 1 GeV, where the…
The Fermi Gamma-ray Space Telescope has revealed a diffuse $\gamma$-ray background at energies from 0.1 GeV to 1 TeV, which can be separated into Galactic emission and an isotropic, extragalactic component. Previous efforts to understand…
The physics of Ultra High Energy Cosmic Rays will be reviewed, discussing the latest experimental results and theoretical models aiming at explaining the observations in terms of spectra, mass composition and possible sources. It will be…
Ultrahigh energy cosmic rays are the most energetic of any subatomic particles ever observed in nature. The quest for their mysterious origin is currently a major scientific challenge. Here we explore the possibility that these particles…