Exciting the TTV Phases of Resonant Sub-Neptunes

Exciting the TTV Phases of Resonant Sub-Neptunes by Nick Choksi et al. on Tuesday 29 November There are excesses of sub-Neptunes just wide of period commensurabilities like the 3:2 and 2:1, and corresponding deficits narrow of them. Any theory that explains this period ratio structure must also explain the strong transit timing variations (TTVs) observed near resonance. Besides an amplitude and a period, a sinusoidal TTV has a phase. Often overlooked, TTV phases are effectively integration constants, encoding information about initial conditions or the environment. Many TTVs near resonance exhibit non-zero phases. This observation is surprising because dissipative processes that capture planets into resonance also damp TTV phases to zero. We show how both the period ratio structure and the non-zero TTV phases can be reproduced if pairs of sub-Neptunes capture into resonance in a gas disc while accompanied by a third non-resonant body. Convergent migration and eccentricity damping drives pairs to orbital period ratios wide of commensurability and, after the disk clears, secular forcing by the third-body perturber phase-shifts the TTVs. The scenario predicts that resonant planets are apsidally aligned and possess eccentricities up to an order of magnitude larger than previously thought. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.15701v1