Related papers: A new code for radiation processes in high energy …
Accreting sources such as AGN, X-ray binaries or gamma-ray bursts are known to be strong, high energy emitters. The hard emission is though to originate from plasmas of thermal and/or non-thermal high energy particles. Not only does this…
Modelling the emission properties of compact high energy sources such as X-ray binaries, AGN or gamma-ray bursts represents a complex problem. Contributions of numerous processes participate non linearly to produce the observed spectra:…
The high energy emission of microquasars is thought to originate from high energy particles. Depending on the spectral state, the distribution of these particles can be thermal with a high temperature (typically 100 keV) or non-thermal and…
Gamma-ray binaries have been uncovered as a new class of Galactic objects in the very high energy sky (> 100 GeV). The three systems known today have hard X-ray spectra (photon index ~ 1.5), extended radio emission and a high luminosity in…
Being the most extreme explosions in the universe, gamma-ray bursts (GRBs) provide a unique laboratory to study various plasma physics phenomena. The complex lightcurve and broad-band, non-thermal spectra indicate a very complicated system…
It is at present well known that conditions at some massive binary systems allow acceleration of particles and production of the GeV-TeV gamma-rays. However, which particles are responsible for this emission and what radiation processes are…
X-ray binaries are composed of a normal star in orbit around a neutron star or stellar-mass black hole. Radio and X-ray observations have led to the presumption that some X-ray binaries called microquasars behave as scaled down active…
Active galactic nuclei (AGN) produce the highest intrinsic luminosities in the Universe from within a compact region. The central engine is thought to be powered by accretion onto a supermassive black hole. A fraction of this huge release…
Various types of active galactic nuclei (AGN) are briefly discussed, with an emphasis on the theory of recent X-ray and $\gamma$-ray observations of the subclass, Seyfert 1 galaxies. The large radiation power from AGN is thought to…
We consider different scenarios of collisions of compact objects (clouds, massive stars, supernova shock waves, or young pulsars) with jets in active galactic nuclei. The purpose is to find out if such collisions can become plausible…
Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales,…
The cores of active galactic nuclei (AGN) harbor some of the most extreme conditions of matter and energy in the Universe. One of the major goals of high-energy astrophysics is to probe these extreme environments in the vicinity of…
Advances in X-ray and gamma-ray astronomy have opened a new window on our universe and revealed a wide variety of binaries composed of a compact object and a Be star. In Be X-ray binaries, a neutron star accretes the Be disk and truncates…
We describe a numerical model constructed for the study of the emission of radiation from relativistic plasma under conditions characteristic, e.g., to gamma-ray bursts (GRB's) and active galactic nuclei (AGN's). The model solves self…
The impact of non-thermal processes on the spectral energy distributions of galaxies can be dramatic, but such processes are often neglected in considerations of their structure and evolution. Particle acceleration associated with high mass…
After initial claims and a long hiatus, it is now established that several binary stars emit high (0.1-100 GeV) and very high energy (>100 GeV) gamma rays. A new class has emerged called 'gamma-ray binaries', since most of their radiated…
Young stars show a variety of highly energetic phenomena, from accretion and outflow processes to hot coronal plasmas confined in their outer atmosphere, all regulated by the intense stellar magnetic fields. Many aspects on each of these…
We point out a few remarkable properties of the $\gamma\gamma\to\gamma\gamma$ process at high energy. They should allow to search for effects of new particles and interactions. We give illustrations with threshold effects due to pairs of…
The study of the hard (E>10 keV) energy spectra of X-ray binary pulsars can give a wealth of information on the physical processes that occur close to the neutron star surface. Extreme matter regimes are probed, and precious information on…
An increasing number of early-type (O and Wolf-Rayet) colliding wind binaries (CWBs) is known to accelerate particles up to relativistic energies. In this context, non-thermal emission processes such as inverse Compton (IC) scattering are…