The phase 0.5 absorption in SW Sextantis-type cataclysmic variables

Abstract

The SW Sextantis stars are a group of cataclysmic variables with distinctive observational characteristics, including absorption features in the emission line cores at phases 0.2-0.6. Hellier and Robinson have proposed that these features are caused by the accretion stream flowing over the accretion disk. However, in a simple model the absorption occurred at all orbital phases, which is contradicted by the data. I show that invoking a flared accretion disk resolves this problem.