We present analytical and numerical solutions for accretion discs subject to a non-zero central torque. express this in terms of single parameter, $f$, which is the ratio outward viscous flux angular momentum from inner boundary inward advected there. The standard "accretion" disc, where condition zero-torque, represented by $f=0$. A "decretion" radial velocity at zero, $f\rightarrow\infty$. Fo...

Calculations of X-ray reflection spectra from ionized, optically-thick material are an important tool in investigations of accretion flows surrounding compact objects. We present the results of reflection calculations that treat the relevant physics with a minimum of assumptions. The temperature and ionization structure of the top five Thomson depths of an illuminated disc are calculated while ...

Non-relativistic, magnetically-driven jets are constructed by taking self-consistently into account the feedback on the underlying accretion disc. It is shown that such jets are mostly described by the ejection index ξ = d ln Ṁa/d ln r, which is a local measure of the disc ejection efficiency. This parameter is found to lie in a very narrow range, due to constraints imposed by both the disc ver...

The thermal reprocessing hypothesis in AGN, where EUV/X-ray photons are reprocessed by the accretion disc into optical/UV photons, predicts wavelength-dependent time delays between the optical continuum at different wavelengths. Recent photometric monitoring by Sergeev et al. has shown that the time-delay is observed in 14 AGN, and generally seen to increase with increasing wavelength, as predi...

Observations of accreting systems often show significant variability (10–20 percent of accretion luminosity) on timescales much longer than expected for the disc regions releasing most of the luminosity. We propose an explicit physical model for disc variability , consistent with Lyubarskii's (1997) general scheme for solving this problem. We suggest that local dynamo processes can affect the e...

We have performed three-dimensional numerical simulations of accretion discs in a close binary system using the Smoothed Particle Hydrodynamics (SPH) method. Our results show that, contrary to previous claims, 3D discs do exist even when the specific heat ratio of the gas is as large as γ = 1.2. Although the disc is clearly more spread in the z-direction in this case than it is for the quasi-is...

We have analyzed the optical and radio properties of a sample of 3CR FR I radio galaxies which have Hubble Space Telescope imaging capable of detecting optical cores. The jet powers of the FR I radio galaxies are estimated from their low-frequency radio luminosities, and the optical core luminosity is taken as an upper limit on the emission from any unobscured accretion disc. We argue that if t...