Orbits and masses of binaries from Speckle Interferometry at SOAR

Abstract

We present results from Speckle inteferometric observations of fifteen visual binaries and one doubleline 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 M down to 0.2 M . 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 M and 0.857 ± 0.026 M ; 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.