Kepler-30: the Cesar of TTV variations
Panichi et al
We study the orbital architecture, physical character of planets, formation and long-term evolution of the Kepler-30 planetary system, detected and announced in 2012 by the KEPLER team. We show that it belongs to a particular class of very compact and quasi-resonant, yet long-term stable planetary systems. We re-analyzed light-curves of the host star spanning Q1-Q17 quarters. A huge variability of the Transit Timing Variations (TTV) exceeding 2 days is induced by a massive Jovian planet located between two Neptune-like companions. The innermost pair is near to the 2:1 mean motion resonance (MMR), and the outermost pair is close to the 19:8 MMR. Our re-analysis of photometric data allows us to constrain better than before the orbital elements, planets' radii and masses, which are 9.2±0.1, 536±5, and 23.7±1.3 Earth masses for Kepler-30b, Kepler-30c and Kepler-30d, respectively. The masses of the inner planets are determined within ∼1% uncertainty. We inferred the internal structures of the Kepler-30 planets and their bulk densities in a wide range from ∼0.19±0.01 g⋅cm−3 for Kepler-30d, ∼0.96±0.15 g⋅cm−3 for Kepler-30b, to ∼1.71±0.13 g⋅cm−3 for Jovian planet Kepler-30c, respectively. We attempt to explain the origin of this unique planetary system and a deviation of the orbits from exact MMRs by the planetary migration scenario. We anticipate that the Jupiter-mass planet plays an important role in determining the present dynamical state of this system.