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Description
Transit Timing Variations (TTVs) can provide useful information for systems observed by transit, by putting constraints on the masses and eccentricities of the observed planets, or even constrain the existence of non-transiting companions. However, TTVs can also act as a detection bias that can prevent the detection of small planets in transit surveys, that would otherwise be detected by standard algorithm such as the Boxed Least Square algorithm (BLS) if their orbit was not perturbed. This bias is especially present for surveys with long baseline, such as Kepler, some of the TESS sectors, and the upcoming PLATO mission. Here we introduce a detection method that is robust to large TTVs, and illustrate it by recovering and confirming a pair of resonant super-Earths with 10 hour TTVs around Kepler-1705 (prev. KOI-4772). The method is based on a neural network trained to recover the tracks of low-SNR perturbed planets in river diagrams. We then recover the transit parameters of these candidates by fitting the lightcurve. The individual transit signal-to-noise of Kepler-1705b and c are about three time smaller than all the previously-known planets with TTVs of 3 hours or more, pushing the boundary in the recovering of these small, dynamically active planets. Recovering this type of object is essential to have a complete picture of the observed planetary systems, solving for a bias not often taken into account in statistical studies of exoplanet populations. In addition, TTVs are a means of obtaining mass estimates which can be essential to studying the internal structure of planets discovered by transit surveys. Finally, we show that due to the strong orbital perturbations, it is possible that the spin of the outer resonant planet of Kepler-1705 is trapped in a sub or super-synchronous spin-orbit resonance. This would have important consequences on the climate of the planet since a non-synchronous spin implies that the flux of the star is spread over the whole planetary surface.
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