In this paper, we study the accretion process for fluids flowing near a black hole in the context of f (T ) teleparallel gravity. Specifically, by performing a dynamical analysis by a Hamiltonian system, we are able to find the sonic points. After that, we consider different isothermal test fluids in order to study the accretion process when they are falling onto the black hole. We find that th...

We solve for the structure of a hot accretion disc with unsaturated thermal Comptonisation of soft photons and with advection, generalizing the classical model of Shapiro et al. The upper limit on the accretion rate due to advection constrains the luminosity to < ∼ 0.15y 3/5 α 7/5 of the Eddington limit, where y and α are the Compton and viscosity parameters, respectively. The characteristic te...

A large-scale closed magnetic field can transfer angular momentum and energy between a black hole (BH) and its surrounding accretion flow. We investigate the effects of this magnetic coupling (MC) process on the dynamics of a hot accretion flow (e.g., an advection dominated accretion flow, hereafter ADAF). The energy and angular momentum fluxes transported by the magnetic field are derived by a...

We present simulations of the accretion of a massive planet or brown dwarf by an AGB star. In our scenario, close planets will be engulfed by the star, spiral-in and be dissipated in the “accretion region” located at the bottom of the convective envelope of the star. The deposition of mass and chemical elements in this region will release a large amount of energy that will produce a significant...

Title of Dissertation: Accretion onto Black Holes from Large Scales Regulated by Radiative Feedback KwangHo Park, Doctor of Philosophy, 2012 Dissertation directed by: Professor Massimo Ricotti Department of Astronomy This thesis focuses on radiation-regulated gas accretion onto black holes (BHs) from galactic scales emphasizing the role of thermal and radiation pressure in limiting gas supply t...

A self-similar solution for the 3D axi-symmetric radiative MHD equations, which revisits the formation and acceleration of accretion-powered jets in AGNs and microquasars, is presented. The model relies primarily on electromagnetic extraction of rotational energy from the disk plasma and forming a geometrically thin super-Keplerian layer between the disk and the overlying corona. The outflowing...

There is a class of dynamos where the eld is caused by a velocity eld which, in turn, is driven by the generated magnetic eld. Numerical three-dimensional simulations of this type of process are reviewed. This process is here discussed in connection with accretion discs, but we point out that similar mechanisms have also been suggested in the context of solar and galactic dynamos. The underlyin...