Geometrical constraints upon the unipolar model of {V407 Vul} and {RX J0806.3+1527}

Abstract

V407 Vul and RX J0806.3+1527 are X-ray emitting stars with X-ray light curves 100% modulated on periods of 569 and 321 seconds respectively. These are the only periods seen, and are thought to be the orbital periods of ultra-compact pairs of white dwarfs. There are two main double white dwarf models: the unipolar inductor model analogous to the Jupiter-Io system and the direct impact model analogous to Algol. We consider geometrical constraints on the unipolar inductor model, in particular what parameter values (component masses, orbital inclination i and magnetic co-latitude beta) can fit the X-ray and optical light curves.