a1 Center for High Angular Resolution Astronomy, Georgia State University, Atlanta, GA, USA email: email@example.com
Long-baseline optical interferometry (LBI) can nearly close the gap in selection space between astrometric and spectroscopic detection of binary star systems, bringing the complementary powers of astrometry and spectroscopy to bear on a complete dynamical understanding of such systems, particularly including the determination of the masses of the individual stellar components. In the case of double-lined spectroscopic systems, their resolution by long-baseline interferometry also yields the orbital parallax and hence the luminosities of the individual stars. In some of these cases, the angular diameters of one or more components are accessible, and so a complete specification of a star in terms of its mass, radius and luminosity is made.
The northern hemisphere is now equipped with several interferometers of unprecedented capability in terms of their baseline sizes, numbers of telescopes and telescope apertures. These instruments, most notably the Palomar Testbed Interferometer at Mt. Palomar Observatory, have produced very significant results of a number of interesting systems fulfilling interferometry's promise to produce fundamental astrophysical data at levels of accuracy that challenge or confirm astrophysical theory.
This paper presents basic principles of long-baseline interferometric study of binary stars and summarizes results from northern interferometers with specific examples of their broad impact on binary star astronomy.