Orbits for eighteen visual binaries and two double-line spectroscopic binaries observed with HRCAM on the CTIO SOAR 4m telescope, using a new Bayesian orbit code based on Markov Chain Monte Carlo

Abstract

We present orbital elements and mass sums for eighteen visual binary stars of spectral types B to K (five of which are new orbits) with periods ranging from 20 to more than 500 yr. For two double-line spectroscopic binaries with no previous orbits, the individual component masses, using combined astrometric and radial velocity data, have a formal uncertainty of ~0.1 MSun. Adopting published photometry, and trigonometric parallaxes, plus our own measurements, we place these objects on an H-R diagram, and discuss their evolutionary status. These objects are part of a survey to characterize the binary population of stars in the Southern Hemisphere, using the SOAR 4m telescope+HRCAM at CTIO. Orbital elements are computed using a newly developed Markov Chain Monte Carlo algorithm that delivers maximum likelihood estimates of the parameters, as well as posterior probability density functions that allow us to evaluate the uncertainty of our derived parameters in a robust way. For spectroscopic binaries, using our approach, it is possible to derive a self-consistent parallax for the system from the combined astrometric plus radial velocity data ("orbital parallax"), which compares well with the trigonometric parallaxes. We also present a mathematical formalism that allows a dimensionality reduction of the feature space from seven to three search parameters (or from ten to seven dimensions - including parallax - in the case of spectroscopic binaries with astrometric data), which makes it possible to explore a smaller number of parameters in each case, improving the computational efficiency of our Markov Chain Monte Carlo code.

32 pages, 9 figures, 6 tables. Detailed Appendix with methodology. Accepted by The Astronomical Journal

References in corpus (10)

• The Gaia mission
• Speckle interferometry at SOAR in 2012 and 2013
• Efficient fitting of multiplanet Keplerian models to radial velocity and astrometry data
• The binarity of Milky Way F,G,K stars as a function of effective temperature and metallicity
• Stellar loci II. a model-free estimate of the binary fraction for field FGK stars
• The Orbit and Mass of the Third Planet in the Kepler-56 System
• Observations of Binary Stars with the Differential Speckle Survey Instrument. V. Toward an Empirical Metal-Poor Mass-Luminosity Relation
• Bayesian analysis of the radial velocities of HD 11506 reveals another planetary companion
• Searching for faint companions with VLTI/PIONIER. II. 92 main sequence stars from the Exozodi survey
• Microlens Masses from 1-D Parallaxes and Heliocentric Proper Motions

Cited by in corpus (7)

• Speckle interferometry at SOAR in 2018
• Orbital elements and individual component masses from joint spectroscopic and astrometric data of double-line spectroscopic binaries
• Observations of Binary Stars with the Differential Speckle Survey Instrument. VIII. Measures of Metal-Poor Stars and Triple Stars from 2015 to 2018
• A celestial matryoshka: Dynamical and spectroscopic analysis of the Albireo system
• Orbits and masses of binaries from Speckle Interferometry at SOAR
• Visual binary stars with partially missing data: Introducing multiple imputation in astrometric analysis
• Bayesian inference in single-line spectroscopic binaries with a visual orbit