As part of our follow-up campaign of Kepler planets , we observed Kepler-117 with the SOPHIE spectrograph at the Observatoire de Haute-Provence .
This F8-type star hosts two transiting planets in non-resonant orbits .
The planets , Kepler-117 b and c , have orbital periods \simeq 18.8 and \simeq 50.8 days , and show transit-timing variations ( TTVs ) of several minutes .
We performed a combined Markov chain Monte Carlo ( MCMC ) fit on transits , radial velocities , and stellar parameters to constrain the characteristics of the system .
We included the fit of the TTVs in the MCMC by modeling them with dynamical simulations .
In this way , consistent posterior distributions were drawn for the system parameters .
According to our analysis , planets b and c have notably different masses ( 0.094 \pm 0.033 and 1.84 \pm 0.18 M _ { J } ) and low orbital eccentricities ( 0.0493 \pm 0.0062 and 0.0323 \pm 0.0033 ) .
The uncertainties on the derived parameters are strongly reduced if the fit of the TTVs is included in the combined MCMC .
The TTVs allow measuring the mass of planet b , although its radial velocity amplitude is poorly constrained .
Finally , we checked that the best solution is dynamically stable .