Tidal decay of circumbinary planetary systems

It is shown that circumbinary planetary systems are subject to universal tidal decay (shrinkage of orbits), caused by the forced orbital eccentricity inherent to them. Circumbinary planets (CBP) are liberated from parent systems, when, owing to the shrinkage, they enter the circumbinary chaotic zone. On shorter timescales (less than the current age of the Universe), the effect may explain, at least partially, the observed lack of CBP of close-enough (with periods < 5 days) stellar binaries; on longer timescales (greater than the age of the Universe but well within stellar lifetimes), it may provide massive liberation of chemically evolved CBP. Observational signatures of the effect may comprise (1) a prevalence of large rocky planets (super-Earths) in the whole population of rogue planets (if this mechanism were the only source of rogue planets); (2) a mass-dependent paucity of CBP in systems of low-mass binaries: the lower the stellar mass, the greater the paucity.