Reaching the boundary between stellar kinematic groups and very wide
  binaries. The Washington Double Stars with the widest angular separations
  Aims. I look for and characterise very wide binaries and multiple systems
with projected physical separations larger than s = 0.1 pc, which is generally
believed to be a sharp upper limit to the distribution of wide binay semimajor
axes. Methods. I investigated in detail 30 Washington Double Stars with angular
separations rho > 1000 arcsec. I discarded 23 of them as probably unbound
systems based on discordant astrometry, photometry, spectral types, and radial
velocities. The remaining seven systems were subject to a comprehensive data
compilation and derivation (multi-wavelength photometry, heliocentric distance,
multiplicity, age, mass, metallicity, membership in young kinematic group).
Results. Of the seven very wide systems, six have projected physical
separations larger than the hypothetical cutoff at s = 0.1 pc; four of them
have separations s > 0.2 pc. Although there are two systems in young kinematic
groups (namely HD 136654 and BD+32 2572 in the Hyades Supercluster, and AU Mic
and AT Mic AB in the beta Pictoris moving group), there is not a clear
prevalence of young systems (tau < 1 Ga) among these very wide binaries.
Finally, I compare the binding energies of the seven systems with those of
other weakly bound systems in the field.
