Two Super-Earths in the 3:2 MMR around KOI-1599

We validate the planetary origin of the KOI-1599 transit time variations (TTVs) with statistical and dynamical tests. We re-analysed KEPLER Q1-Q17 light-curves of the star, and we independently derived the TTVs. They appear as strongly anticorrelated, suggestive of two mutually interacting planets. We found similar radii of the candidates, 1.9 +/- 0.2R(circle plus) for the inner KOI-1599.02, and 1.9 +/- 0.3R(circle plus) for the outer KOI-1599.01. The standard MCMC TTV analysis constrains the planet masses safely below the dynamical instability limit of similar or equal to 3 M-Jup. The best-fitting MCMC model yields (9.0 +/- 0.3) M-circle plus, and (4.6 +/- 0.3) M-circle plus, for the inner and the outer planet, respectively. The planets are trapped in 3: 2 mean motion resonance (MMR) with anti-aligned apsides (Delta(omega) over bar = 180 degrees) at low-eccentric (e similar or equal to 0.01) orbits. However, we found that the TTV mass determination depends on eccentricity priors with the dispersion in the (0.01,0.05) range. They permit a second family of TTV models with smaller masses of similar or equal to 7 M-circle plus, and similar or equal to 3.6 M-circle plus, respectively, exhibiting two modes of Delta(omega) over bar = 0 degrees, 180 degrees librations. The 3: 2 MMR is dynamically robust and persists for both modes. In order to resolve the mass duality, we re-analysed the TTV data with a quasi-analytic model of resonant TTV signals. This model favours the smaller masses. We also reproduced this model by simulating the migration capture of the system into the 3: 2 MMR.