This paper studied the relativistic accretion thick disc model raised by a deformed compact object that slightly deviated from spherical up to the quadrupole moment by utilising $\rm q$-metric. This metric is the simplest asymptotically flat solution of Einstein's equation with quadrupole moment. This work aims to study the effects of quadrupole moments in combination with the parameters of the thick magnetised disc model via studying the properties of these equilibrium sequences of magnetised, non-self-gravitating discs in this space-time. We employed different angular momentum distributions and discussed the procedure of building this toroidal disc model based on a combination of approaches previously considered in the literature. We have shown the properties of this relativistic accretion disc model and its dependence on the initial parameters. Besides, this theoretical model can be served as the initial data for numerical simulations.
We present the first family of magnetically polarized equilibrium tori around a Kerr black hole. The models were obtained in the test fluid approximation by assuming that the tori is a linear media, making it is possible to characterize the magnetic polarization of the fluid through the magnetic susceptibility $χ_{m}$. The magnetohydrodynamic (MHD) structure of the models was solved by following the Komissarov approach, but with the aim of including the magnetic polarization of the fluid, the integrability condition for the magnetic counterpart was modified. We build two kinds of magnetized to…
We investigate the local stability of strongly magnetized relativistic tori orbiting Kerr black holes, for the case of a purely toroidal magnetic field topology. Our approach encompasses both solving the full dispersion relation numerically and solving a simplified analytic treatment. Both approaches indicate that such tori are subject to an unstable non-axisymmetric magnetorotational mode, regardless of such background properties as the gas-to-magnetic pressure ratio and specific angular momentum distribution. We demonstrate that our modal analysis matches well with what is seen in global, th…
Hot accretion tori around a compact object are known to be susceptible to a global hydrodynamical instability, the so-called Papaloizou-Pringle (PP) instability, arising from the interaction of non-axisymmetric waves across the corotation radius, where the wave pattern speed matches the fluid rotation rate. However, accretion tori produced in various astrophysical situations (e.g., collapsars and neutron star binary mergers) are likely to be highly magnetized. We study the effect of magnetic fields on the PP instability in incompressible tori with various magnetic strengths and structures. In …
We present an analytical approach for the equilibrium of a self-gravitating charged fluid embedded in a spherical gravitational and dipolar magnetic fields produced by a central mass. Our scheme is proposed, as a toy-model, in the context of gaseous/dusty tori surrounding supermassive black holes in galactic nuclei. While the central black hole dominates the gravitational field and it remains electrically neutral, the surrounding material has a non-negligible self-gravitational effect on the torus structure. By charging mechanisms it also acquires non-zero electric charge density, so the two i…
We present new equilibrium solutions of stationary models of magnetized thick disks (or tori) around Kerr black holes with synchronised scalar hair. The models reported here largely extend our previous results based on constant radial distributions of the specific angular momentum along the equatorial plane. We introduce a new way to prescribe the distribution of the disk's angular momentum based on a combination of two previous proposals and compute the angular momentum distribution outside the equatorial plane by resorting to the construction of von Zeipel cylinders. We find that the effect …
We analyzed the effects of a toroidal magnetic field in the formation of several magnetized accretion tori, dubbed as ringed accretion disks (RADs), orbiting around one central Kerr supermassive Black Hole (SMBH) in AGNs, where both corotating and counterotating disks are considered. Constraints on tori formation and emergence of RADs instabilities, accretion onto the central attractor and tori collision emergence, are investigated. The results of this analysis show that the role of the central BH spin-mass ratio, the magnetic field and the relative fluid rotation and tori rotation with respec…
Testing the true nature of black holes - the no-hair hypothesis - will become increasingly more precise in the next few years as new observational data is collected in both the gravitational wave channel and the electromagnetic channel. In this paper we consider numerically generated spacetimes of Kerr black holes with synchronised scalar hair and build stationary models of magnetized thick disks (or tori) around them. Our approach assumes that the disks are not self-gravitating, they obey a polytropic equation of state, the distribution of their specific angular momentum is constant, and they…
We discuss the conditions for the existence of extended matter configurations orbiting in the ergoregion or close to the outer ergosurface of the Kerr black hole ("dragged" configurations). The corotating tori under consideration are perfect fluid configurations with barotropic equation of state, orbiting on the equatorial plane of the central Kerr black hole. The possibility of magnetized tori with a toroidal magnetic field is also discussed. Indications on the attractors where dragged tori can be observed are provided with the analysis of the fluid characteristics and geometrical features, r…
We present stationary solutions of geometrically thick discs (or tori) endowed with a self-consistent toroidal magnetic field distribution surrounding a non-rotating black hole in an analytical, static, spherically-symmetric $f(R)$-gravity background. These $f(R)$-gravity models introduce a Yukawa-like modification to the Newtonian potential, encoded in a single parameter $δ$ which controls the strength of the modified potential and whose specific values affect the disc configurations when compared to the general relativistic case. Our models span different magnetic field strengths, from purel…
Ringed accretion disks (RADs) are aggregates of corotating and counterrotating toroidal accretion disks orbiting a central Kerr super-massive Black Hole (SMBH) in AGNs. The dimensionless spin of the central BH and the fluids relative rotation are proved to strongly affect the RAD dynamics. There is evidence of a strict correlation between SMBH spin, fluid rotation and magnetic fields in RADs formation and evolution. Recently, the model was extended to consider RADs constituted by several magnetized accretion tori and the effects of a toroidal magnetic field in RAD dynamics have been investigat…
We discuss the effects of electric charging on the equilibrium configurations of magnetized, rotating fluid tori around black holes of different mass. In the context of gaseous/dusty tori in galactic nuclei, the central black hole dominates the gravitational field and it remains electrically neutral, while the surrounding material acquires some electric charge and exhibits non-negligible self-gravitational effect on the torus structure. The structure of the torus is influenced by the balance between the gravitational and electromagnetic forces. A cusp may develop even in Newtonian tori due to …
Accreting neutron stars are one of the main targets for continuous gravitational wave searches, as asymmetric accretion may lead to quadrupolar deformations, or `mountains', on the crust of the star, which source gravitational wave emission at twice the rotation frequency. The gravitational wave torque may also impact on the spin evolution of the star, possibly dictating the currently observed spin periods of neutron stars in Low Mass X-ray Binaries and leading to the increased spindown rate observed during accretion in PSR J1023+0038. Previous studies have shown that deformed reaction layers …
Runaway instability operates in fluid tori around black holes. It affects systems close to the critical (cusp overflowing) configuration. The runaway effect depends on the radial profile l(R) of the angular momentum distribution of the fluid, on the dimension-less spin a of the central black hole, and other factors, such as self-gravity. Previously it was demonstrated that, for the power-law dependence of the radial angular momentum profile, non-magnetized tori always become runaway stable for a sufficiently high positive value of q. Here we discuss the role of runaway instability within a fra…
