• DOI:10.1051/0004-6361/200912596
• Corpus ID: 118194112

Reaching the boundary between stellar kinematic groups and very wide binaries - The Washington double stars with the widest angular separations

@article{Caballero2009ReachingTB,
  title={Reaching the boundary between stellar kinematic groups and very wide binaries - The Washington double stars with the widest angular separations},
  author={Jos{\'e} A. Caballero},
  journal={Astronomy and Astrophysics},
  year={2009},
  volume={507},
  pages={251-259}
}

• J. Caballero
• Published 19 August 2009
• Physics
• Astronomy and Astrophysics

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 binary semimajor axes. Methods. I investigated in detail 30 Washington double stars with angular separations of ρ > 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 a young kinematic group). Results. Of the seven very wide systems, six have projected physical separations greater than the hypothetical cutoff at $s = 0.1$ pc and four 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 β  Pictoris moving group), there is no clear prevalence of young systems ( τ < 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.