How we can learn from studies of wide binary statistics

Summary We present a versatile technique for comparing wide binary observations with theoretical semi-major axis distributions. To illustrate this technique, the theoretical implications of the recent Lathamet al. (1984) data on wide binaries are examined. We conclude that power law models for the underlying distribution are consistent with observations, implying no sharp cut-offs in the semi-major axis distribution. We argue that the detection of 6 wide binaries by Lathamet al. would require an uncomfortably large local density of wide binaries (semi-major axesa≳10⁻³ pc) for a broad range of theoretical models. Motivated by the apparent high number density of wide binaries implied by the Lathamet al. sample, we define a criterion for selecting candidate wide binaries form theYale Bright Star Catalog. The candidate list is used to determine an upper bound for wide binary density ofn _WB=4×10⁻³ pc⁻³. Although the actual value is somewhat uncertain, there is no difficulty in principle in reconciling this result with the local stellar number density.