Eccentricity distribution of wide binaries

Speed and direction of the relative motion are determined from the short observed arcs or known orbits, and their joint distribution is compared to the numerical simulations. By inverting the observed distribution with the help of simulations, we find that average eccentricity of wide binaries is 0.59+/-0.02 and the eccentricity distribution can be modelled as f(e)~1.2e+0.4.

However, wide binaries containing inner subsystems, i.e. triple or higher order multiples, have significantly smaller eccentricities with the average e=0.52+/-0.05 and the peak at e~0.5. We find that the catalogue of visual orbits is strongly biased against large eccentricities. A marginal evidence of eccentricity increasing with separation (or period) is found for this sample.