ExoFit: Orbital Parameters of Extra-solar Planets from Radial Velocities

Abstract

Retrieval of orbital parameters of extrasolar planets poses considerable statistical challenges.Due to sparse sampling, measurement errors, parameters degeneracy and modelling limitations, there are no unique values of basic parameters, such as period and eccentricity. Here, we estimate the orbital parameters from radial velocity data in a Bayesian framework by utilizing Markov Chain Monte Carlo (MCMC) simulations with the Metropolis-Hastings algorithm. We follow a methodology recently proposed by Gregory and Ford. Our implementation of MCMC is based on the object-oriented approach outlined by Graves. We make our resulting code, ExoFit, publicly available with this paper. It can search for either one or two planets as illustrated on mock data. As an example we re-analysed the orbital solution of companions to HD 187085 and HD 159868 from the published radial velocity data. We confirm the degeneracy reported for orbital parameters of the companion to HD 187085, and show that a low-eccentricity orbit is more probable for this planet. For HD 159868, we obtained slightly different orbital solution and a relatively high 'noise' factor indicating the presence of an unaccounted signal in the radial velocity data. ExoFit is designed in such a way that it can be extended for a variety of probability models, including different Bayesian priors.

Accepted to MNRAS, 11 pages, 10 figures. Minor changes in Section 2, Appendix removed . ExoFit can be downloaded from http://www.star.ucl.ac.uk/~lahav/exofit.html

References in corpus (11)

• Cosmological parameters from CMB and other data: a Monte-Carlo approach
• Catalog of Nearby Exoplanets
• Improving the Efficiency of Markov Chain Monte Carlo for Analyzing the Orbits of Extrasolar Planets
• Quantifying the Uncertainty in the Orbits of Extrasolar Planets
• The Lick Planet Search: Detectability and Mass Thresholds
• The Rossiter-McLaughlin effect and analytic radial velocity curves for transiting extrasolar planetary systems
• Detectability of Extrasolar Planets in Radial Velocity Surveys
• The HARPS search for southern extra-solar planets I. HD330075 b: a new 'hot Jupiter'
• Asteroseismology of the planet-hosting star $\mu$ Arae. I. The acoustic spectrum
• High eccentricity planets from the Anglo-Australian Planet Search
• New Planets around Three G Dwarfs

Cited by in corpus (26)

• Inferring the eccentricity distribution
• Detecting extrasolar planets from stellar radial velocities using Bayesian evidence
• RUN DMC: An efficient, parallel code for analyzing Radial Velocity Observations using N-body Integrations and Differential Evolution Markov chain Monte Carlo
• Observational biases in determining extrasolar planet eccentricities in single-planet systems
• Bayesian analysis of radial velocity data of GJ667C with correlated noise: evidence for only 2 planets
• The Hunt for Exomoons with Kepler (HEK): III. The First Search for an Exomoon around a Habitable-Zone Planet
• Importance Gaussian Quadrature
• An Ultra Metal-poor Star Near the Hydrogen-burning Limit
• A 4-Planet System Orbiting the K0V Star HD 141399
• Compressed Monte Carlo with application in particle filtering
• Rotating Stars and Revolving Planets: Bayesian Exploration of the Pulsating Sky
• HADES RV Programme with HARPS-N at TNG: V. A super-Earth on the inner edge of the habitable zone of the nearby M-dwarf GJ 625
• Qatar-1: indications for possible transit timing variations
• Directed follow-up strategy of low-cadence photometric surveys in Search of transiting exoplanets - I. Bayesian approach for adaptive scheduling
• The Lick-Carnegie Exoplanet Survey: Gliese 687b: A Neptune-Mass Planet Orbiting a Nearby Red Dwarf
• An Integrated Analysis of Radial Velocities in Planet Searches
• The HARPS search for southern extra-solar planets XLV. Two Neptune mass planets orbiting HD 13808: a study of stellar activity modelling's impact on planet detection
• Improved Point Source Detection in Crowded Fields using Probabilistic Cataloging
• A super-Earth orbiting the nearby M-dwarf GJ 536
• A Uniformly Derived Catalogue of Exoplanets from Radial Velocities
• Variational Inference as an alternative to MCMC for parameter estimation and model selection
• Bayesian evidence for two companions orbiting HIP 5158
• Bayesian Methods for Analysis and Adaptive Scheduling of Exoplanet Observations
• Nii: a Bayesian orbit retrieval code applied to differential astrometry
• Spectroscopic Study of the Circularly Polarised Radio Source TYC 2834-1385-1: An Active Binary
• Improving exoplanet mass characterisation with Bayesian model selection using the Learned Harmonic Mean Estimator