Theoretical X-ray power spectra of intermediate polars

Abstract

We compute the power spectra of the X-ray modulations expected from intermediate polars in various accretion geometries. Discless accretion models produce a richer variety of power spectra, and are hard to rule out by comparison with observation. In particular, the presence of strong spin modulations and the absence of spin-orbit beat modulations is compatible with such geometries. The presence of beat-frequency modulations is incompatible with dominant accretion via a disc.