Multiple Stars in the Field

Abstract

When examining the statistics of multiple stars in the field, especially coming from visual binary star point of view, several problems present themselves. First, and most importantly, is distinguishing between physical multiples and optical pairs. Establishing physicality is not a simple ”binary” response as there are degrees of certainty. We discuss some of the reasons for caring about non-physical pairs, as well as the tools for establishing or more correctly identifying apparent kinematic properties which hopefully result in dynamic solutions. The Washington Double Star Catalog, the Visual Orbit Catalog, and the US Naval Observatory speckle program are used as examples in many of these cases. The magnum opus for a global characterization of these systems is the Washington Multiplicity Catalog (WMC). Selected as a catalog and a method to ”develop a simple, unambiguous, flexible, and computer friendly designation scheme for stellar companions (including planets)” at a multi-commission meeting in Manchester (GA24). This was re-affirmed at Special Session 3 in Sydney (GA25) by Commissions 5, 8, 26, 42, 45 and the Working Group on Interferometry when a sample (1/2 hour band) WMC was produced. An all-sky WMC is in progress the binary sources utilized in its construction and the implications resulting from it with regards to multiple stars in the field are discussed.