Key words accretion, accretion discs – black hole physics – galaxies: active – relativity – X-rays: general The inner parts of black-hole accretion discs shine in X-rays which can be monitored and the observed spectra can be used to trace strong gravitational fields in the place of emission and along paths of light rays. This paper summarizes several aspects of how the spectral features are inf...

Intermediate polars range from systems which accrete entirely via discs (e.g. EX Hya) through systems which combine disc and disc-overrow accretion (e.g. FO Aqr) to discless accretors (e.g. RX 1712{ 24). The accretion curtain model provides a good description of the optical spin-pulses, while in the X-ray regime, occultation combines with absorption to create complex pulse-prooles.

An axisymmetric model of a cool, dynamo-active accretion disc is applied to protostellar discs. Thermally and magnetically driven outflows develop that are not collimated within 0.1AU. In the presence of a central magnetic field from the protostar, accretion onto the protostar is highly episodic, which is in agreement with earlier work.