Kepler-93b is a 1.478 ± 0.019 R ⊕ planet with a 4.7 day period around a bright (V = 10.2), astroseismically-characterized host star with a mass of 0.911 ± 0.033 M ⊙ and a radius of 0.919 ± 0.011 R ⊙ . Based on 86 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we present a precise mass estimate of 4.02 ± 0.68 M ⊕ . The corresponding high density of 6.88 ± 1.18 g/cc is consistent with a rocky composition of primarily iron and magnesium silicate. We compare Kepler-93b to other dense planets with well-constrained parameters and find that between 1 − 6 M ⊕ , all dense planets including the Earth and Venus are well-described by the same fixed ratio of iron to magnesium silicate. There are as of yet no examples of such planets with masses > 6 M ⊕ : All known planets in this mass regime have lower densities requiring significant fractions of volatiles or H/He gas. We also constrain the mass and period of the outer companion in the Kepler-93 system from the long-term radial velocity trend and archival adaptive optics images. As the sample of dense planets with well-constrained masses and radii continues to grow, we will be able to test whether the fixed compositional model found for the seven dense planets considered in this paper extends to the full population of 1 − 6 M ⊕ planets. Subject headings: planetary systems -planets and satellites: composition -stars: individual (Kepler-93 = KOI 69 = KIC 3544595) -techniques: radial velocities * Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

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 ∼3 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 planetplanet scattering, Kozai-Lidov perturbations, or secular chaos. The distribution of α = 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 α > 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 au have modified tidal quality factors 10 5 Q p 10 9 , and that stellar Q s 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 +0.021 −0.018 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. of giant planets are still open questions. Among these are the migration of hot Jupiters, the origin of the frequently observed spin-orbit misalignments, and the architecture of planetary systems with closein giant planets. These planets are thought to be formed beyond the water-ice line (a 1−3 au) in the protoplanetary disc, where solid material is abundant because of ice condensation, Article published by EDP Sciences A107, page 1 of 16 A&A 602, A107 (2017)

Recent analyses 1-4 of data from the NASA Kepler spacecraft 5 have established that planets with radii within 25 per cent of Earth's (R⊕) are commonplace throughout the Galaxy, orbiting at least 16.5 per cent of Sun-like stars 1 . Because these studies were sensitive to the sizes of the planets but not their masses, the question remains whether these Earth-sized planets are indeed similar to the Earth in bulk composition. The smallest planets for which masses have been accurately determined 6,7 are Kepler-10b (1.42R⊕) and Kepler-36b (1.49R⊕), which are both significantly larger than the Earth. Recently, the planet Kepler-78b was discovered 8 and found to have a radius of only 1.16R⊕. Here we report that the mass of this planet is 1.86 Earth masses. The resulting mean density of the planet is 5.57 g cm −3 , which is similar to that of the Earth and implies a composition of iron and rock.Every 8.5 h, the star Kepler-78 (first known as TYC 3147-188-1 and later designated KIC 8435766) presents to Earth a shallow eclipse consistent 8 with the passage of an orbiting planet with a