The Extended R CrA Young Association

Observing ROSAT sources in an area covering ~30% of the Southern Hemisphere, including the R CrA Association, we found evidences that this nearby association may be much larger than previously thought. Although in the survey we found many young stars near the R CrA, there are 20 young stars with properties that characterize them as possibly belonging to the R CrA association. From the nine known members with measured proper motions and radial velocities, we obtain the mean space velocity components for the Association relative to the Sun: (U, V, W) = (-3.8 +/- 1.2, -14.3 +/- 1.7, -8.3 +/- 2.0$)km/s. The new young stars with similar space velocities are in a projected diameter of ~35deg. At a distance of ~100pc, this represents a size of ~60pc, similar to the spread in the kinematical distances obtained assuming the above space velocity components. If the original velocity dispersion during star formation was equal to the dispersion of the velocity vector moduli (~3km/s), then the age of the association should be ~10Myr to reach this size. In this way, the classical T Tauri spectroscopic binary V4046 Sgr could be a member of the association.