Catálogo de publicaciones - libros

We have performed 3-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations of jet formation from an accretion disk with/without initial perturbation around a rotating black hole. We input a sinusoidal perturbation (m=5 mode) in the rotation velocity of the accretion disk. The simulation results show the formation of a relativistic jet from the accretion disk. Although the initial perturbation becomes weakened by the coupling among different modes, it survives and triggers lower modes. As a result, complex non-axisymmetric density structure develops in the disk and the jet. Newtonian MHD simulations of jet formation with a non-axisymmetric mode show the growth of the m=2 mode but GRMHD simulations cannot see the clear growth of the m=2 mode.

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 plausible mechanism to generate the observed structures.

We analyse the effects of central AGN heating on the formation of galaxy clusters by means of hydrodynamical simulations. Besides self-gravity of dark matter and baryons, our approach includes radiative cooling and heating processes of the gas component and a multiphase model for a self-consistent treatment of star formation and SNe feedback [1]. Additionally, we incorporate a periodic feedback mechanism in the form of hot buoyant bubbles, injected into the ICM during the active phases of accreting central AGN. We find that AGN heating can substantially affect the properties of the stellar and gaseous components, in particular reducing the mass deposition rate onto the central cD galaxy, thereby offering an energetically plausible solution to the cooling flow problem.

There is strong evidence that the observed kHz Quasi Periodic Oscillations (QPOs) in the X-ray flux of neutron star and black hole sources in LMXRBs are linked to Einstein’s General Relativity. Abramowicz & Klu’zniak (2001) suggested a non-linear resonance model to explain the QPOs origin: here we summarize their idea and the development of a mathematical toy-model which begins to throw light on the nature of Einstein’s gravity non-linear oscillations.

Shear flows are ubiquitous phenomena in astrophysical environments. We present recent results concerning the acceleration of energetic particles in turbulent shear flows showing that cosmic ray particles can be accelerated efficiently in the relativistic jets of AGNs and GRBs. Efficient cosmic ray acceleration results in an induced flow viscosity that may explain part of the deceleration effects observed.

In this work we discuss two different types of models for the high-energy gamma-ray production in microquasars. On the one hand, we introduce a new leptonic model where the emission arises from inverse Compton interactions with both internal (synchrotron) and external photon fields, and relativistic Bremsstrahlung from interactions with cold protons in the jet and the stellar wind material. On the other hand, we introduce a hadronic model where the gamma rays are the result of interactions between relativistic protons in the jet and cold protons from the anisotropic stellar wind. Spectral differences and similarities between both types of models are briefly discussed.

The propagation of electromagnetic signals of pulsars through the non-stationary gravitational field of the stellar globular clusters formed by an ensemble of arbitrarily distributed stars are discussed. The expression for the relativistic time delay of pulsars radiation in such fields are derived taking into account the negligible aberration corrections. The obtained results are considered in the application to the globular cluster NGC 104 (Tucanae 47) for the cases of the small and large impact parameters.

We use two models in order to deal with a rotating universe. The first one is a thin rotating spherical shell. When we introduce in this shell an Hydrogen atom we found that the gravitomagnetic field of this universe can split the energy levels of the atom in a way analogous to the Zeeman effect.

The second model is the Gödel universe. There we use the solution of the Dirac equation on an arbitrary spacetime to find the shifts on energy levels of Hydrogen atoms caused by the rotation of the universe.

In both cases the interaction energy is very small, so we have to study the effect of cosmic rotation on Hydrogen atoms in a rotating expanding universe.

The main conclusions of the accretion induced neutron star magnetic field evolution model are described, and it is found that a bright Z source possesses a stronger field than that of on Atoll source and local strong field may exist in the recycled neutron stars or millisecond pulsars on account of the field line distribution.

We analyse the effects of central AGN heating on the formation of galaxy clusters by means of hydrodynamical simulations. Besides self-gravity of dark matter and baryons, our approach includes radiative cooling and heating processes of the gas component and a multiphase model for a self-consistent treatment of star formation and SNe feedback [1]. Additionally, we incorporate a periodic feedback mechanism in the form of hot buoyant bubbles, injected into the ICM during the active phases of accreting central AGN. We find that AGN heating can substantially affect the properties of the stellar and gaseous components, in particular reducing the mass deposition rate onto the central cD galaxy, thereby offering an energetically plausible solution to the cooling flow problem.