Rapid Oscillations in Cataclysmic Variables. XIV. Orbital and Spin Ephemerides of FO Aquarii

Abstract

ABSTRACTWe report on 17 years of photometry of FO Aquarii, a cataclysmic variable with a rapidly rotating, magnetic white dwarf. We give ephemerides for its variations at the 4.8 hr binary period and the 21 minute spin period. The orbital period is constant at 0.2020596(1) day. The spin period decreases on a timescale of 106 yr, but with additional wiggles on timescales of years to decades. The observed alternation between spin‐down and spin‐up suggests that the star is near its equilibrium spin period, an important prediction of the theory of magnetic cataclysmic variables.