Resolved double-lined spectroscopic binaries

Spectroscopic binaries resolved visually allow us to obtain the orbital parallaxes (as well as masses and other parameters) of both components without involving any assumptions about their nature. Orbital parallax is the only way, apart from trigonometric parallax, to directly determine (rather than estimate) the distance to the star. A comprehensive catalog of resolved spectroscopic binaries contains orbital elements, multicolor photometry, and astrophysical parameters for 173 systems. A comparison of trigonometric and orbital parallaxes shows that the latter are preferred in a certain range of large semi-major axis (a>26–27 AU) and brightness ( V > 9–10 mag). Also, we present the most promising systems from the SB9 catalogue in terms of resolution into components.