We carried out a Bayesian homogeneous determination of the orbital parameters of 231 transiting giant planets ( TGPs ) that are alone or have distant companions ; we employed differential evolution Markov chain Monte Carlo methods to analyse radial-velocity ( RV ) data from the literature and 782 new high-accuracy RVs obtained with the HARPS-N spectrograph for 45 systems over \sim 3Â years .
Our work yields the largest sample of systems with a transiting giant exoplanet and coherently determined orbital , planetary , and stellar parameters . We found that the orbital parameters of TGPs in non-compact planetary systems are clearly shaped by tides raised by their host stars .
Indeed , the most eccentric planets have relatively large orbital separations and/or high mass ratios , as expected from the equilibrium tide theory .
This feature would be the outcome of planetary migration from highly eccentric orbits excited by planet-planet scattering , Kozai-Lidov perturbations , or secular chaos .
The distribution of \alpha = a / a _ { R } , where a and a _ { R } are the semi-major axis and the Roche limit , for well-determined circular orbits peaks at 2.5 ; this agrees with expectations from the high-eccentricity migration ( HEM ) , although it might not be limited to this migration scenario .
The few planets of our sample with circular orbits and \alpha > 5 values may have migrated through disc-planet interactions instead of HEM .
By comparing circularisation times with stellar ages , we found that hot Jupiters with a < 0.05 Â au have modified tidal quality factors 10 ^ { 5 } \lesssim Q ^ { \prime } _ { p } \lesssim 10 ^ { 9 } , and that stellar Q ^ { \prime } _ { s } \gtrsim 10 ^ { 6 } -10 ^ { 7 } are required to explain the presence of eccentric planets at the same orbital distance . As a by-product of our analysis , we detected a non-zero eccentricity e = 0.104 _ { -0.018 } ^ { +0.021 } for HAT-P-29 ; we determined that five planets that were previously regarded to be eccentric or to have hints of non-zero eccentricity , namely CoRoT-2b , CoRoT-23b , TrES-3b , HAT-P-23b , and WASP-54b , have circular orbits or undetermined eccentricities ; we unveiled curvatures caused by distant companions in the RV time series of HAT-P-2 , HAT-P-22 , and HAT-P-29 ; we significantly improved the orbital parameters of the long-period planet HAT-P-17c ; and we revised the planetary parameters of CoRoT-1b , which turned out to be considerably more inflated than previously found .