Observed orbital eccentricities for 391 binaries

As has been found by others, those binaries with periods of a few days have been circularized. However, those with periods up to about 1000 or more days show reduced eccentricities that asymptotically approach a mean value of 0.5 for the longest periods.

For those binaries with periods greater than 1000 days their distribution of eccentricities is flat from 0 to nearly 1, indicating that in the formation of binaries there is no preferential eccentricity. The binaries with intermediate periods (10-100 days) lack highly eccentric orbits.