Related papers: X-rays and Gamma-rays from Cataclysmic Variables: …
Evidence for nonthermal activity in clusters of galaxies is well established from radio observations of synchrotron emission by relativistic electrons, and new windows (in EUV and Hard X-ray ranges) have provided more powerful tools for its…
In the last few years the Fermi -LAT instrument has detected GeV gamma-ray emission from a few novae. Such GeV emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. It is expected that…
Some massive binaries should contain energetic pulsars which inject relativistic leptons from their inner magnetospheres and/or pulsar wind regions. If the binary system is compact enough, then these leptons can initiate inverse Compton…
High-energy cosmic rays can be accelerated in clusters of galaxies, by mega-parsec scale shocks induced by accretion of gas during the formation of large-scale structure, or by powerful sources harbored in clusters. Once accelerated, the…
In this chapter we consider the processes which can lead to X-ray emission from different types of cataclysmic variable stars (CVs). CVs are semi-detached, binary star systems where material is transferred from the donor star (also known as…
We discuss the consequences of almost rectilinear acceleration of protons to extremely high energies in a reconnection region on the surface of an accretion disk which surrounds a central black hole in an active galaxy. The protons produce…
We study the synchrotron radiation as the observed non-thermal X-ray emission from old pulsars ($\gtrsim1-10$Myr) to investigate the particle acceleration in their magnetospheres. We assume that the power-law component of the observed X-ray…
The Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously. Low-luminosity active galactic nuclei have…
The Compton Gamma Ray Observatory revealed the high energy emission of some Active Galactic Nuclei called "Blazars"; few of them have also been observed by ground Cererenkov arrays. Those sources observed with Whipple Observatory emit gamma…
Current generation of ground based gamma-ray telescopes observed dozens of sources of photons above 100 TeV. Supernova remnants, pulsar wind nebulae, young stellar clusters and superbubbles are considered as possible sites of PeV-regime…
Radio observations discovered large scale non thermal sources in the central Mpc regions of dynamically disturbed galaxy clusters (radio halos). The morphological and spectral properties of these sources suggest that the emitting electrons…
We study high-energy emission from the mergers of neutron star binaries as electromagnetic counterparts to gravitational waves aside from short gamma-ray bursts. The mergers entail significant mass ejection, which interacts with the…
Shocks arising in galaxy mergers could accelerate cosmic-ray (CR) ions to TeV-PeV energies. While propagating in the intergalactic medium, these CRs can produce high-energy neutrinos, electron-positron pairs and gamma-rays. In the presence…
The HESS collaboration recently reported highly significant detection of TeV gamma-rays coincident with Sgr A*. In the context of other Galactic Center (GC) observations, this points to the following scenario: In the extreme…
The extension of the cosmic-ray (CR) spectrum well beyond 1~PeV necessitates the existence of a population of accelerators in the Milky Way, which we refer to as Super PeVatrons. Identifying the nature of these sources remains a challenge…
We discuss recent observations of high energy cosmic ray positrons and electrons in the context of hadronic interactions in supernova remnants, the suspected accelerators of galactic cosmic rays. Diffusive shock acceleration can harden the…
We aim at characterizing a sample of 9 new hard X-ray selected Cataclysmic Variable (CVs), to unambiguously identify them as magnetic systems of the Intermediate Polar (IP) type. We performed timing and spectral analysis by using X-ray, and…
The detection of diffuse radio emission associated with clusters of galaxies indicates populations of relativistic leptons infusing the intracluster medium. Those electrons and positrons are either injected into and accelerated directly in…
The current detectors of gamma-ray emission specially at TeV energies have too poor resolution to determine whether this emission is produced in the jet or in the core, particularly of low luminous, non-blazar AGNs (like radio galaxies). In…
Context. White dwarfs (WDs) in cataclysmic variables (CVs) are important experimental laboratories where the electron degeneracy is taking place on a macroscopic scale. Magnetic CVs increase in number especially in the hard X-ray band (>10…