Search for wide binaries in the Yale Bright Star Catalogue

Abstract

The authors define specific criteria for identifying candidate wide binaries in the Yale Bright Star Catalogue. These criteria select all pairs of stars with projected angular separations of Δθ &lt; θ<SUB>0</SUB> and relative proper motions Δμ &lt; μ<SUB>0</SUB>, where θ<SUB>0</SUB> and μ<SUB>0</SUB> are arbitrarily chosen cutoffs. The authors present a list of candidate pairs with θ<SUB>0</SUB> = 10arcmin and μ<SUB>0</SUB> =0arcsec.01 yr<SUP>-1</SUP> and discuss the statistics of candidates with θ<SUB>0</SUB> as large as 1°. To assess the significance of these indentifications, the authors compute the expected background due to random associations that would result if there were no actual pairwise correlations. For this purpose the Bahcall-Soneira Galaxy model is applied. The authors present evidence for clustering on relatively large scales that is unlikely to be due to binaries. Their results can be most plausibly ascribed to bound or currently dissolving open clusters with core radii ≡1 pc. Interpreting their candidate list as a superposition of wide binaries and coincident pairs of cluster members, the authors estimate that the number density of wide binaries n<SUB>WB</SUB> ⪉ 5% of the stellar density in the solar neighborhood.