The galactic black hole binary systems give an observational template showing how the accretion flow changes as a function of increasing mass accretion rate, or L/LEdd. These data can be synthetised with theoretical models of the accretion flow to give a coherent picture of accretion in strong gravity, in which the major hard-soft spectral transition is triggered by a change in the nature and g...

We present a model which relates the width of the Broad Emission Lines of AGN to the Keplerian velocity of an accretion disk at a critical distance from the central black hole. This critical distance falls in a region bounded on the inward side by the transition radius between the radiation pressure and the gas pressure dominated region of the accretion disk and on the outward side by the maxim...

We present self-similar solutions for advection-dominated accretion flows with radial viscous force in the presence of outflows from the accretion flow or infall. The axisymmetric flow is treated in variables integrated over polar sections and the effects of infall and outflows on the accretion flow are parametrised for possible configurations compatible with the self-similar solution. We inves...

The formation of massive stars may take place at relatively low accretion rates over a long period of time if the accretion can continue past the onset of core hydrogen ignition. The accretion may continue despite the formation of an ionized HII region around the star if the HII region is small enough that the gravitational attraction of the star dominates the thermal pressure of the HII region...

We calculate the jet power of the classical Blandford-Znajek (BZ) model and hybrid model developed by Meier (2001) based on the global solutions of advection dominated accretion flows (ADAFs) surrounding Kerr black holes. We find that the jet power of the hybrid model is larger than that of the pure BZ model. The jet power will dominate over the accretion power and the objects will enter into “...

N -body simulations predict that CDM halo-assembly occurs in two phases: 1) a rapid accretion phase dominated by major mergers with a rapidly deepening potential well; and 2) a slow accretion phase characterised by a gentle addition of mass to the outer halo with little change in the inner potential well. We demonstrate, using onedimensional simulations, that this two-phase accretion leads to C...

Spherical (nonrotating) accretion flows with small-scale magnetic fields have been investigated using three-dimensional, time-dependent MHD simulations. These simulations have been designed to model high-resolution (quasi) steady accretion flows in a wedge computational domain that represents a small fraction of the full spherical domain. Subsonic and supersonic (super-fast-magnetosonic) accret...

We examine the conditions imposed on the vertical structure of accretion discs for them to exist. We find that a wind powered by a thermal instability exists in all discs with certain opacity laws. We find that for discs dominated by bremsstrahlung radiation, an inner hole develops below a certain accretion rate, and that for very low accretion rates, discs may not form at all. The consequences...