Observational biases in determining extrasolar planet eccentricities in single-planet systems

Abstract

We investigate potential biases in the measurements of exoplanet orbital parameters obtained from radial velocity observations for single-planet systems. We create a mock catalog of radial velocity data, choosing input planet masses, periods, and observing patterns from actual radial velocity surveys and varying input eccentricities. We apply Markov Chain Monte Carlo (MCMC) simulations and compare the resulting orbital parameters to the input values. We find that a combination of the effective signal-to-noise ratio of the data, the maximal gap in phase coverage, and the total number of periods covered by observations is a good predictor of the quality of derived orbit parameters. As eccentricity is positive definite, we find that eccentricities of planets on nearly circular orbits are preferentially overestimated, with typical bias of 1-2 times the median eccentricity uncertainty in a survey (e.g., 0.04 in the Butler et al. 2006 catalog). When performing population analysis, we recommend using the mode of the marginalized posterior eccentricity distribution to minimize potential biases. While the Butler et al. (2006) catalog reports eccentricities below 0.05 for just 17% of single-planet systems, we estimate that the true fraction of e < 0.05 orbits is about f(0.05)=38\pm 9%. For planets with P > 10 days, we find f(0.05)=28\pm 8% versus 10% from Butler et al. (2006). These planets either never acquired a large eccentricity or were circularized following any significant eccentricity excitation.

21 pages, including 8 b/w figures, 4 color figures and 2 tables. Accepted to MNRAS

References in corpus (14)

• Dynamical Outcomes of Planet-Planet Scattering
• Formation of Hot Planets by a combination of planet scattering, tidal circularization, and Kozai mechanism
• Origins of Eccentric Extrasolar Planets: Testing the Planet-Planet Scattering Model
• Efficient fitting of multiplanet Keplerian models to radial velocity and astrometry data
• On the Eccentricity Distribution of Exoplanets from Radial Velocity Surveys
• On The Origins Of Eccentric Close-in Planets
• Close encounters in young stellar clusters: implications for planetary systems in the solar neighbourhood
• Planet-planet scattering in planetesimal disks
• Long-Period Objects in the Extrasolar Planetary Systems 47 UMa and 14 Her
• A Bayesian Kepler Periodogram detects a second planet in HD 208487
• Selection Functions in Doppler Planet Searches
• On the origin of eccentricities among extrasolar planets
• ExoFit: Orbital Parameters of Extra-solar Planets from Radial Velocities
• Determination Of The Orbit Of The Planetary Companion To The Metal Rich Star HD 45350

Cited by in corpus (51)

• The Occurrence and Architecture of Exoplanetary Systems
• The Minimum-Mass Extrasolar Nebula: In-Situ Formation of Close-In Super-Earths
• A dynamically-packed planetary system around GJ667C with three super-Earths in its habitable zone
• Parametrizing the exoplanet eccentricity distribution with the Beta distribution
• Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
• Kepler Planet Masses and Eccentricities from TTV Analysis
• Consequences of the Ejection and Disruption of Giant Planets
• Steady-state planet migration by the Kozai-Lidov mechanism in stellar binaries
• The statistics of multi-planet systems
• Bayesian search for low-mass planets around nearby M dwarfs. Estimates for occurrence rate based on global detectability statistics
• The Distribution of Transit Durations for Kepler Planet Candidates and Implications for their Orbital Eccentricities
• $\beta$ Pictoris' inner disk in polarized light and new orbital parameters for $\beta$ Pictoris b
• Planet-Planet Scattering Alone Cannot Explain the Free-Floating Planet Population
• HD 285507b: An Eccentric Hot Jupiter in the Hyades Open Cluster
• Debris disks as signposts of terrestrial planet formation. II Dependence of exoplanet architectures on giant planet and disk properties
• Advances in exoplanet science from Kepler
• Increased Tidal Dissipation Using Advanced Rheological Models: Implications for Io and Tidally Active Exoplanets
• Synthesizing Exoplanet Demographics: A Single Population of Long-Period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys
• Color difference makes a difference: four planet candidates around tau Ceti
• An Empirically Derived Three-Dimensional Laplace Resonance in the Gliese 876 Planetary System
• Origins of Hot Jupiters from the Stellar Obliquity Distribution
• An Affine-Invariant Sampler for Exoplanet Fitting and Discovery in Radial Velocity Data
• Architectures of Planetary Systems and Implications for their Formation
• Suppression of type I migration by disk winds
• The Solar System as an Exoplanetary System
• BD+48 740 - Li overabundant giant star with a planet. A case of recent engulfment?
• Bias and robustness of eccentricity estimates from radial velocity data
• The Demographics of Rocky Free-Floating Planets and their Detectability by WFIRST
• Host star metallicity of directly imaged wide-orbit planets: implications for planet formation
• A Novel Method to Photometrically Constrain Orbital Eccentricities: Multibody Asterodensity Profiling (MAP)
• Secular Orbital Evolution of Compact Planet Systems
• Bringing "The Moth" to Light: A Planet-Sculpting Scenario for the HD 61005 Debris Disk
• Evidence for Two Hot Jupiter Formation Paths
• Synthesizing Exoplanet Demographics from Radial Velocity and Microlensing Surveys, I: Methodology
• WASP-54b, WASP-56b and WASP-57b: Three new sub-Jupiter mass planets from SuperWASP
• The curious case of HD41248. A pair of static signals buried behind red-noise
• An Apodized Kepler Periodogram for Separating Planetary and Stellar Activity Signals
• On the Orbital Inclination of Proxima Centauri b
• Determining Exoplanetary Oblateness Using Transit Depth Variations
• The SNR of a Transit
• Stability Constrained Characterization of Multiplanet Systems
• RV-exoplanet eccentricities: Good, Beta, and Best
• Planetary Orbit Eccentricity Trends (POET). I. The Eccentricity-Metallicity Trend for Small Planets Revealed by the LAMOST-Gaia-Kepler Sample
• Secular Behavior of Exoplanets: Self-Consistency and Comparisons with the Planet-Planet Scattering Hypothesis
• Resilient habitability of nearby exoplanet systems
• Signals embedded in the radial velocity noise
• The debris disk - terrestrial planet connection
• Angular momentum distributions for observed and modeled exoplanetary systems
• The HD 217107 Planetary System: Twenty Years of Radial Velocity Measurements
• The Transits of Extrasolar Planets with Moons
• A Homogeneous Catalog of Rossiter-McLaughlin Systems: Distinct $e$-$\lambda$ Trends in Three Gas-Giant Mass Regimes