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.