A complete sample of wide binaries in the solar neighborhood

In wide binaries the large separations between the component stars results in these systems being very sensitive to encounters with the constituents of the Galaxy. This sensitivity has been capitalized upon by theoretical models to probe the nature and the density of matter in the Galactic disk. However, to make the predictions of these models meaningful a well-defined complete sample of unambiguously bound wide binaries is required. Here such a sample is presented. Initially a well-defined candidate list of suspected wide binaries was compiled. Accurate radial-velocity measurements were made for all systems wider than 10^-3 pc in projected separation s in the list. Based on these observed radial velocities it is determined whether these systems are physically associated. The resulting sample appears complete for physical systems where s>0.32 mpc, M_v <9.0, π≥0.040 arcsec, and δ> - 12°. The sample contains 39 systems of which ∼41% are hierarchical systems. The distribution of the separations from the sample obeys a simple power law relation. No physical systems wider than 0.1 pc are detected, and a sharp cutoff in number density is indicated at ∼0.1 pc. However, a power law fit without a sharp cutoff cannot be rejected with confidence. Based on the sample, number densities for wide binaries are calculated as a function of separation. It appears that ∼3% of local stars should be members of systems wider than 0.01 pc. The sample indicates that the components in a wide system could have been drawn from the local luminosity function independent of each other's spectral type.