Orbits of Double Stars from Long Baseline Optical Interferometry
Session 86 -- Double Stars
Display presentation, Friday, January 14, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [86.04] Orbits of Double Stars from Long Baseline Optical Interferometry

C.A.Hummel, J.T.Armstrong (USRA)

The spectroscopic binary observing program of the Mark III Optical Interferometer has produced six published orbits and twenty preliminary orbits. The mean precision is 0.3\% for measurements of $\sin i$ and 0.7\% for measurements of the semimajor axis $a$. These orbits represent more than half of the systems with detected nightly visibility variations in excess of about 20\%, corresponding to a pair of unresolved components with a magnitude difference of not more than 2.4 magnitudes. By the same criterion, we detected indications of multiplicity in about half of the stars we had selected from catalogs of spectroscopic binaries with predicted major axes between 3 mas and 40 mas, $m_{\rm V} < 5$, $\delta > -10^\circ$, and for which we had obtained a sufficient amount of data.

We describe our data analysis, which features direct fitting of the orbital elements and component parameters to the measured visibilities, as well as our uncertainty analysis based on Monte Carlo simulations.

We present results on some of the binaries, notably a very high precision orbit of Capella with the component diameters determined, and sub-10-mas angular scale orbits of $\beta$ Aurigae, $\pi$ Andromedae, $\theta$ Aquilae, $\beta$ and $\delta$ Trianguli. We discuss some of the results in terms of stellar evolution theory.