Synchrotron emitting Komissarov torus with magnetic polarization around Kerr black holes

Abstract

ABSTRACT Magnetic fields in black hole accretion discs are associated with processes of mass accretion and energy amplification. The contribution of the magnetic field due to the magnetic polarization of the material induces effects on the physical properties of the medium that have repercussions on the radiation coming from the accretion discs. Hence, from observations, it could be possible to infer the ‘fingerprint’ left by the magnetic polarization of the material and establish the properties of the space–time itself. As the first step in this purpose, we use numerical simulations to systematically analyse the possible observable effects produced by the magnetic properties of an accretion disc around a Kerr black hole. We found that under the synchrotron radiation power-law model the effects of the magnetic polarization are negligible when the plasma is gas pressure-dominated. Nevertheless, as beta-plasma decreases, the emission becomes more intense for magnetic pressure-dominated discs. In particular, we found that paramagnetic discs emit the highest intensity value independent of the beta-plasma parameter in this regime. By contrast, the emitted flux decreases with the increase of beta-plasma due to the dependence of the magnetic field on the emission and absorption coefficients. Moreover, the disc morphology changes with the magnetic susceptibility: Paramagnetic discs are more compact than diamagnetic ones. This fact leads to diamagnetic discs emitting a greater flux because each photon has a more optical path to travel inside the disc.