Search results for "Astrophysical jet"
showing 10 items of 67 documents
Physical Parameters in the Hot Spots and Jets of Compact Symmetric Objects
2001
We present a model to determine the physical parameters of jets and hot spots of a sample of CSOs under very basic assumptions like synchrotron emission and minimum energy conditions. Based on this model we propose a simple evolutionary scenario for these sources assuming that they evolve in ram pressure equilibrium with the external medium and constant jet power. The parameters of our model are constrained from fits of observational data (radio luminosity, hot spot radius and hot spot advance speed) versus projected linear size. From these plots we conclude that CSOs evolve self-similarly and that their radio luminosity increases with linear size along the first kiloparsec. Assuming that t…
Observational Effects of Anomalous Boundary Layers in Relativistic Jets
2008
Recent theoretical work has pointed out that the transition layer between a jet an the medium surrounding it may be more complex than previously thought. Under physically realizable conditions, the transverse profile of the Lorentz factor in the boundary layer can be non-monotonic, displaying the absolute maximum where the flow is faster than at the jet spine, followed by an steep fall off. Likewise, the rest-mass density, reaches an absolute minimum (coincident with the maximum in Lorentz factor) and then grows until it reaches the external medium value. Such a behavior is in contrast to the standard monotonic decline of the Lorentz factor (from a maximum value at the jet central spine) an…
Does the plasma composition affect the long term evolution of relativistic jets?
2001
We study the influence of the matter content of extragalactic jets on their morphology, dynamics and emission properties. For this purpose we consider jets of extremely different compositions including pure leptonic and baryonic plasmas. Our work is based on two-dimensional relativistic hydrodynamic simulations of the long-term evolution of powerful extragalactic jets propagating into a homogeneous environment. The equation of state used in the simulations accounts for an arbitrary mixture of electrons, protons and electron-positron pairs. Using the hydrodynamic models we have also computed synthetic radio maps and the thermal Bremsstrahlung X-ray emission from their cavities. Although ther…
Resonant Kelvin-Helmholtz modes in sheared relativistic flows
2007
Qualitatively new aspects of the (linear and non-linear) stability of sheared relativistic (slab) jets are analyzed. The linear problem has been solved for a wide range of jet models well inside the ultrarelativistic domain (flow Lorentz factors up to 20; specific internal energies $\approx 60c^2$). As a distinct feature of our work, we have combined the analytical linear approach with high-resolution relativistic hydrodynamical simulations, which has allowed us i) to identify, in the linear regime, resonant modes specific to the relativistic shear layer ii) to confirm the result of the linear analysis with numerical simulations and, iii) more interestingly, to follow the instability develo…
Analytical and Numerical Studies of Fluid Instabilities in Relativistic Jets
2007
Relativistic outflows represent one of the best-suited tools to probe the physics of AGN. Numerical modelling of internal structure of the relativistic outflows on parsec scales provides important clues about the conditions and dynamics of the material in the immediate vicinity of the central black holes in AGN. We investigate possible causes of the structural patterns and regularities observed in the parsec-scale jet of the well known quasar 3C 273. We compare the model with the radio structure observed in 3C 273 on parsec scales using very long baseline interferometry (VLBI) and constrain the basic properties of the flow. Our results show that Kelvin-Helmholtz instabilities are the most p…
Which physical parameters can be inferred from the emission variability of relativistic jets?
2005
We present results of a detailed numerical study and theoretical analysis of the dynamics of internal shocks in relativistic jets and the non-thermal flares associated with these shocks. In our model internal shocks result from collisions of density inhomogeneities (shells) in relativistic jet flows. We find that the merged shell resulting from the inelastic collision of shells has a complicated internal structure due to the non-linear dynamics of the interaction. Furthermore, the instantaneous efficiency for converting kinetic energy into thermal energy is found to be almost twice as high as theoretically expected during the period of significant emission. The Lorentz factors of the intern…
Physical properties of the jet in 0836+710 revealed by its transversal structure(Corrigendum)
2011
Perucho & Lobanov (2007) (PL07, from now on) presented results demonstrating that the jet in 0836+710 has a significant velocity shear layer. These authors used a set of jet parameters found by Lobanov et al. (1998) (including Lorentz factor γ = 11, Mach number Mj = 6, and jet/ambient medium density ratio ρj/ρa = 0.04). They studied different characteristic wavelengths that may develop in a jet with both a thin ( 10% of the jet radius) and a thick shear-ayer ( 60% of the jet radius). The result showed that the observed wavelengths in the jet structure could be more easily explained in terms of a transversally stratified jet. A mistake was, however made in PL07: the equation used to convert …
Radio afterglow of the jetted tidal disruption event Swift J1644+57
2012
The recent transient event Swift J1644+57 has been interpreted as resulting from a relativistic outflow, powered by the accretion of a tidally disrupted star onto a supermassive black hole. This discovery of a new class of relativistic transients opens new windows into the study of tidal disruption events (TDEs) and offers a unique probe of the physics of relativistic jet formation and the conditions in the centers of distant quiescent galaxies. Unlike the rapidly-varying γ/X-ray emission from Swift J1644+57, the radio emission varies more slowly and is well modeled as synchrotron radiation from the shock interaction between the jet and the gaseous circumnuclear medium (CNM). Early after th…
Hydrodynamical and Emission Simulations of Relativistic Jets: Stability and Generation of Superluminal and Stationary Components
2001
We present 2D hydrodynamical and emission simulations of the jet stabilityafter the introduction of strong perturbations on a relativistic jet. These simulations show that the interaction of a single strong perturbation with the underlying jet results in the formation of multiple conical shocks with very specific observational properties.
Interstellar travel guide: Chronicles of a violent universe
2016
In contrast to observations from our local viewpoint, the universe is extremely violent. Explosions of massive stars, X-ray and gamma-ray binary stars, and active galaxies are related to the presence of compact objects such as neutron stars or black holes. Processes such as matter accretion or the formation and release of relativistic plasma jets are responsible for the generation of large amounts of high-energy radiation, caused by the acceleration of elementary particles, and have a significant impact in their surroundings. Moreover, they are related to the generation of gravitational waves: vibrations in spacetime produced by the acceleration of compact massive objects that produce stron…