SOPHIE velocimetry of Kepler transit candidates X. K01-142 c: first radial velocity confirmation of a non-transiting exoplanet discovered by transit timing

The exoplanet KO.1-1.42b (Kepler-88b) shows transit timing variations (TIVs) with a semi-amplitude of similar to 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 similar to 10.92 days and a radius of similar to 0.36 R-Jup. 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. K01-142c, with a mass of 0.626 +/- 0.03 M-Jup, and a period of 22.3397(-0.0018)(+0.0021) days, whi.ch is close to the 2:1 mean-motion resonance with the inner transiting planet. We report an independent confirmation of KO.1-142c 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 0.76(0.16)(+0.32) Map, 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 TI'Vs technique.