SOPHIE velocimetry of Kepler transit candidates - X. KOI-142?c: first radial velocity confirmation of a non-transiting exoplanet discovered by transit timing

摘要

The exoplanet KOI-142b (Kepler-88b) shows transit timing variations (TTVs) with a semi-amplitude of ~12?h, which earned it the nickname “king of transit variations”. Only the transit of planet b was detected in the Kepler data with an orbital period of ~10.92?days and a radius of ~0.36 RJup. The TTVs together with the transit duration variations of KOI-142b were analysed recently, finding a unique solution for a companion-perturbing planet. An outer non-transiting companion was predicted, KOI-142c, with a mass of 0.626?±?0.03 MJup and a period of 22.3397-0.0018+0.0021 days, which is close to the 2:1 mean-motion resonance with the inner transiting planet. We report an independent confirmation of KOI-142c using radial velocity observations with the SOPHIE spectrograph at the Observatoire de Haute-Provence. We derive an orbital period of 22.10?±?0.25?days and a minimum planetary mass of 0.760.16+0.32 MJup, both in good agreement with the predictions by previous transit timing analysis. Therefore, this is the first radial velocity confirmation of a non-transiting planet discovered with TTVs, providing an independent validation of the TTVs technique.