Abstract
A significant number of X-ray binaries are now known to exhibit long-term periodicities on timescales of ∼ 10 - 100 days. Several physical mechanisms have been proposed that give rise to such periodicities, one of which is radiation-driven warping and precession of the accretion disk. Recent theoretical work predicts the stability to disk warping as a function of the mass ratio, binary radius, viscosity and accretion efficiency. We investigate the stability of the superorbital periodicities in the neutron star X-ray binaries Cyg X-2, LMC X-4, SMC X-1 and Her X-1, and thereby confront stability predictions with observation. We find that the period and nature of the superorbital variations in these sources is consistent with the predictions of warping theory.
