Greatly Enhanced Eccentricity Oscillations in Quadruple Systems Composed of Two Binaries: Implications for Stars, Planets, and Transients

We study the orbital evolution of hierarchical quadruple systems composed of two binaries on a long mutual orbit, where each binary acts as a Kozai–Lidov (KL) perturber on the other. We find that the coupling between the two binaries qualitatively changes the behaviour of their KL cycles. The binaries can experience coherent eccentricity oscillations as well as excursions to very high eccentricity...