Orbits and masses of binaries from Speckle Interferometry at SOAR

TL;DR

This study uses speckle interferometry at SOAR to determine orbits and masses of nearby binary stars, providing new orbital data, mass estimates, and a combined astrometric/radial velocity orbit for a spectroscopic binary.

Contribution

It introduces a comprehensive survey of binary systems with orbital solutions and mass estimates, including the first combined orbit for a double-line spectroscopic binary using self-consistent fitting.

Findings

Orbital periods range from 5 to over 500 years.

Masses span from about 0.2 to over 4 solar masses.

The combined orbit for YSC8 matches Gaia parallax very closely.

Abstract

We present results from Speckle inteferometric observations of fifteen visual binaries and one double-line spectroscopic binary, carried out with the HRCam Speckle camera of the SOAR 4.1 m telescope. These systems were observed as a part of an on-going survey to characterize the binary population in the solar vicinity, out to a distance of 250 parsec. We obtained orbital elements and mass sums for our sample of visual binaries. The orbits were computed using a 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 their uncertainty. Their periods cover a range from 5 yr to more than 500 yr; and their spectral types go from early A to mid M - implying total system masses from slightly more than 4 MSun down to 0.2 MSun. They are located at distances between approximately 12 and 200 pc, mostly at low Galactic latitude. For the double-line spectroscopic binary YSC8 we present the first combined astrometric/radial velocity orbit resulting from a self-consistent fit, leading to individual component masses of 0.897 +/- 0.027 MSun and 0.857 +/- 0.026 MSun; and an orbital parallax of 26.61 +/- 0.29 mas, which compares very well with the Gaia DR2 trigonometric parallax (26.55 +/- 0.27 mas). In combination with published photometry and trigonometric parallaxes, we place our objects on an H-R diagram and discuss their evolutionary status. We also present a thorough analysis of the precision and consistency of the photometry available for them.