Absolute magnitudes of cataclysmic variables

Abstract

Absolute magnitudes Mv of the accretion discs (with allowance for effects of inclination) of stars in the principal classes of cataclysmic variable stars are derived from a variety of techniques. For dwarf novae, whose distances are found mostly from infrared observations of their secondaries, a tight relationship is found between Mv(max) at maximum of outburst and orbital period: Mv(max) = 5.64 - 0.259 P(hr). Use of this equation provides Mv(min) at minimum light for further dwarf novae without known distances. For many of these stars it is possible also to derive Mv(mean), averaged over the outburst cycle. Analysis of this extensive data set discloses that MV(min) and MV(mean) are functions of orbital period P and mean time Tn between normal outbursts. An amplitude -Tn(Kukarkin-Parenago) relationship is found to exist for the dwarf novae. A scenario is given in which recent suggestions on cyclical evolution through classical novae, dwarf novae and nova-like variables are shown to agree qualitatively with the systematics found in this study.