A link between X-ray variability and absorption in active galactic nuclei

A Compton heated wind from an accretion disc can cool into dense clouds when the central luminosity temporarily decreases. By reducing the radiation pressure the ionization parameter can be reduced to the critical value below which the hot phase cannot be maintained. In the model presented here, the wind strength is determined by the time-averaged X-ray heating of the disc surface whereas the wind's thermal properties are controlled by the instantaneous radiation spectrum. The model predicts flaring events and constrains the spectral shape - both ultimately testable. (author)