The population statistics of binary stars are an important output of star formation models .
However populations of wide binaries evolve over time due to interactions within a system ’ s birth environment and the unfolding of wide , hierarchical triple systems .
Hence the wide binary populations observed in star forming regions or OB associations may not accurately reflect the wide binary populations that will eventually reach the field .
We use Gaia DR2 data to select members of three open clusters , Alpha Per , the Pleiades and Praesepe and to flag cluster members that are likely unresolved binaries due to overluminosity or elevated astrometric noise .
We then identify the resolved wide binary population in each cluster , separating it from coincident pairings of unrelated cluster members .
We find that these clusters have an average wide binary fraction in the 300-3000 AU projected separation range of 2.1 \pm ^ { 0.4 } _ { 0.2 } % increasing to 3.0 \pm ^ { 0.8 } _ { 0.7 } % for primaries with masses in the 0.5–1.5 M _ { \odot } range .
This is significantly below the observed field wide binary fraction , but shows some wide binaries survive in these dynamically highly processed environments .
We compare our results with another open cluster ( the Hyades ) and two populations of young stars that likely originated in looser associations ( Young Moving Groups and the Pisces-Eridanus stream ) .
We find that the Hyades also has a deficit of wide binaries while the products of looser associations have wide binary fractions at or above field level .