B0849
Title: Binary stars: uniformity, ambiguity and selection
Authors: Peter Jupp - University of St Andrews (United Kingdom) [presenting]
Richard Arnold - Victoria University of Wellington (New Zealand)
Abstract: A binary star is a close pair of stars orbiting around their common centre of mass. Whether the planes of binary star orbits have a common alignment is a question of astronomical interest. Observations are often limited by ambiguity: the direction of the orbital pole (the directed normal to the orbital plane) cannot be distinguished from its reflection in the plane of the sky. Tests of uniformity are presented here that are modifications of Sobolev tests on the sphere. These tests also allow for possible selection effects, in which binary stars may be more or less likely to be detected due to the inclinations of their orbits as seen from the Earth. Rayleigh and Gine tests are applied to data from a standard catalogue of orbits of visual binary stars. Despite the wide scattering of orbital poles, there is consistent evidence of a lack of uniformity and some evidence of a common alignment of orbits of binaries that are more than 20 parsecs from the Sun.
