Soft X-ray emission from Dwarf Novae

Abstract

Dwarf novae are binary systems in which material is being transferred from a low mass main sequence star, via an accretion disc to a white dwarf companion. The two suggested regions of soft X-ray production are the 'hot spot' where the stream of transferred matter strikes the disc and the boundary layer where the accretion disc grazes the surface of the white dwarf. These two possibilities are investigated and it is concluded that the 'hot spot' gives rise to little or no soft X-ray emission, whereas the boundary layer can emit up to half the accretion luminosity as soft X-rays. The structure of the boundary layer delineated here is of relevance to other stellar systems which contain an accretion disc.