Spin modulated X-ray emission from intermediate polars.

This paper describes a comparative study of all the intermediate polars observed by Exosat. The X-ray pulse profiles of each source are presented, and it is shown that, in all cases, the modulation can be described in terms of an increasing depth with decreasing energy. By considering the pulse phase-resolved spectra, it is shown that the modulation cannot be due to simple phase dependent absorption alone, but that models which combine photoelectric absorption with an effect due to self occultation to produce the modulation can explain the data. In addition, models using partial covering of the X-ray emission region produce an improved fit to the overall dataset. To account for the behavior seen, a picture of the accretion process is presented using a structured accretion flow and emission region. In this model, the absorption and occultation effects act in phase and both arise at the same pole of the white dwarf.