On the influence of equilibrium tides on transit-timing variations of close-in super-Earths. I. Application to single-planet systems and the case of K2-265 b

Abstract

In this work, we investigate the influence of planetary tidal interactions on the transit-timing variations of short-period low-mass rocky exoplanets. For such purpose, we employ the recently-developed creep tide theory to compute tidally-induced TTVs. We implement the creep tide in the recently-developed Posidonius N-body code, thus allowing for a high-precision evolution of the coupled spin-orbit dynamics of planetary systems. As a working example for the analyses of tidally-induced TTVs, we apply our version of the code to the K2-265 b planet. We analyse the dependence of tidally-induced TTVs with the planetary rotation rate, uniform viscosity coefficient and eccentricity. Our results show that the tidally-induced TTVs are more significant in the case where the planet is trapped in non-synchronous spin-orbit resonances, in particular the 3/2 and 2/1 spin-orbit resonant states. An analysis of the TTVs induced separately by apsidal precession and tidally-induced orbital decay has allowed for the conclusion that the latter effect is much more efficient at causing high-amplitude TTVs than the former effect by 2 - 3 orders of magnitude. We compare our findings for the tidally-induced TTVs obtained with Posidonius with analytical formulations for the transit timings used in previous works, and verified that the results for the TTVs coming from Posidonius are in excellent agreement with the analytical formulations. These results show that the new version of Posidonius containing the creep tide theory implementation can be used to study more complex cases in the future. For instance, the code can be used to study multiplanetary systems, in which case planet-planet gravitational perturbations must be taken into account additionally to tidal interactions to obtain the TTVs.