The GAPS Programme with HARPS-N at TNG

Abstract

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)

An Apparently Eccentric Orbit of the Exoplanet WASP-12 b as a Radial Velocity Signature of Planetary-induced Tides in the Host Star

“…Considering the above, we used the jitter value of 7.4 m s −1 in further analysis. We note that using the single-night estimate of the jitter or the conservative value from Bonomo et al (2017) does not change our quantitative conclusions.…”

“…Additional data obtained with HARPS-N were taken from Bonomo et al (2017). Those precise observations were performed within a framework of the Global Architecture of Planetary Systems (GAPS) Consortium (Poretti et al 2016) between 2012 and 2015.…”

“…Therefore this quantity may contain not only the physical stellar jitter, but also variations from still-undetected planets and components of instrumental and methodological origin (Isaacson & Fischer 2010;Meunier & Lagrange 2019). The stellar jitter for WASP-12 was found to be equal to 9.1 +1.8 −1.3 m s −1 by Bonomo et al (2017) who used all RV measurements available then and treated jitter as a free parameter while fitting an orbital solution. We noticed, however, that in the case of WASP-12 the jitter is reduced if lower quality data are iteratively rejected.…”

Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System*

“…Bonomo et al (2017) reconsidered all of the available observations of the WASP-18 system obtaining lower limits to the modified tidal quality factors of the star Q in WASP-18 that implies that dynamical tides are likely not excited into the star, as suggested by Ogilvie & Lin (2007). The absence of a detectable tidal decay of the orbit of WASP-18b supports this conclusion (Wilkins et al 2017).…”

The GAPS Programme at TNG

“…However, we caution that the large uncertainties in the efficiency of tidal dissipation inside hot Jupiters and their host stars prevent us from drawing conclusions in any single case (cf. Bonomo et al 2017). We aim at extending the sample of useful systems through our GAPS project.…”