Related papers: Gamma rays from jets interacting with BLR clouds i…
We have developed a model for gamma ray emission in jets of active galactic nuclei in which particle acceleration takes place at a shock in the relativistic jet plasma due to a massive star in the central region of the host galaxy moving…
We study the interaction of early-type stars with the jets of active galactic nuclei. A bow-shock will form as a consequence of the interaction of the jet with the winds of stars and particles can be accelerated up to relativistic energies…
We propose a model to explain the ultra-bright GeV gamma-ray flares observed from the blazar \c454. The model is based on the concept of a relativistic jet interacting with compact gas condensations produced when a star (red giant) crosses…
The production site of gamma rays in blazars is closely related to their interaction with the photon fields surrounding the active galactic nucleus. In this paper, we discuss an indirect method that may help to unveil the presence of…
Flaring activity in blazars can last for vastly different time-scales, and may be the result of density enhancements in the jet flow that result from the intrusion of an interstellar cloud into the jet. We investigate the lightcurves…
We investigate the dissipation of the bulk kinetic energy of a relativistic jet at different distances from the central power--house and analyse in detail how the dissipated energy is radiated away. We assume that the location of the…
The gamma-ray emission of blazar jets shows a pronounced variability and this feature provides limits to the size and to the speed of the emitting region. We study the gamma-ray variability of bright blazars using data from the first 18…
Most of the electromagnetic output of blazars (BL Lac objects and Flat Spectrum Radio Quasars) comes out in the gamma-ray band, making the Large Area Telescope [0.1-100 GeV] onboard the Fermi satellite and the Cherenkov telescopes crucial…
The highest-energy blazars exhibit non-thermal radiation extending beyond 1 TeV with high luminosities and strong variabilities, indicating extreme particle acceleration in their relativistic jets. The gamma-ray spectra of blazars contain…
Extragalactic jets are formed close to supermassive black-holes in the center of galaxies. Large amounts of gas, dust, and stars cluster in the galaxy nucleus, and interactions between this ambient material and the jet base should be…
The exact location of the $\gamma$-ray emitting region in blazar jets has long been a matter of debate. However, the location has important implications about the emission processes, geometric and physical parameters of the jet, as well as…
We present the result obtained from a study, based on long-slit spectroscopy, of the kinematics and ionization mechanisms of the line-emitting gas for a sample of four high/intermediate-redshift radio galaxies. In two of the galaxies (3C352…
We have investigated how several parameters can affect the results of a collision between an extragalactic jet and a dense, intergalactic cloud, through a series of hydrodynamic simulations. Such collisions are often suggested to explain…
As powerful gamma-ray engines, blazars -- relativistic plasma jets launched toward Earth from active galactic nuclei -- are manifestly high-energy particle accelerators. Yet, exactly how these jets accelerate particles as well as what they…
Locating the gamma-ray emission sites in blazar jets is a long-standing and highly controversial issue. We investigate jointly several constraints on the distance scale r and Lorentz factor Gamma of the gamma-ray emitting regions in…
We study the kinematical and brightness evolution of emission line clouds in the narrow line region (NLR) of Seyfert galaxies during the passage of a jet. We derive a critical density above which a cloud remains radiative after compression…
One of the most intriguing and challenging quests of current astrophysics is to understand the physical conditions and processes responsible for production of high-energy particles, and emission of \gamma-rays. A combination of…
The association of at least some long gamma-ray bursts with type Ic supernova explosions has been established beyond reasonable doubt. Theoretically, the challenge is to explain the presence of a light hyper-relativistic flow propagating…
In this work, we compiled a sample of 202 Fermi/LAT blazars with available broad line emissions. Out of the 202 sources, 66 have known Doppler factors. The correlation between ($\gamma$-ray) and broad-line emission, and that between radio…
With their jet pointing towards us, blazars are ideal tools to study the physics and structure of extragalactic jets. Their powerful jets are cosmic particle accelerators and are alleged to be one of the production sites of the high-energy…