Binary star orbits from speckle interferometry

Probably the most well known result of speckle interferometry is the determination of properties of binary stars at or near the diffraction limit of telescopes. This has resulted in a powerful synergy between short-period visual binaries and long-period spectroscopic binaries, resulting in stellar masses and more effective characterization of the empirical mass-luminosity relation for stars. In addition to the ability to reach the diffraction limit of a telescope, interferometry has given a significant improvement in precision of measurement. With careful calibration this precision can be effectively utilized yielding typical errors of 0 degrees.5 in position angle and 0.5% in separation. The timebase of routine speckle interferometric observations of binary stars is now in excess of twenty years. As a result of this Pong series of observations, which are of exceptional accuracy and precision, binary star orbits once considered definitive when based on classical techniques (typically, filar micrometry), are now being further refined, resulting in significant changes in the orbital elements. A typical reduction technique is to use all data associated with a system to determine the orbital period of the binary and then use only high-angular resolution data to determine the other six orbital elements. While these high-angular resolution data include, for example, the historical interferometry work of Schwarzschild, the Anderson and Merrill beam interferometer, and recent results from the ESA Hipparcos satellite, the vast majority come from speckle interferometry. Improvements to the orbital elements based on these data, coupled with the parallaxes from the Hipparcos program, are yielding masses for these binaries with smaller errors.