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Search for associations containing young stars (SACY). I. Sample and searching method
We report results from a high-resolution optical spectroscopic surveyaimed to search for nearby young associations and young stars amongoptical counterparts of ROSAT All-Sky Survey X-ray sources in theSouthern Hemisphere. We selected 1953 late-type (B-V~≥~0.6),potentially young, optical counterparts out of a total of 9574 1RXSsources for follow-up observations. At least one high-resolutionspectrum was obtained for each of 1511 targets. This paper is the firstin a series presenting the results of the SACY survey. Here we describeour sample and our observations. We describe a convergence method in the(UVW) velocity space to find associations. As an example, we discuss thevalidity of this method in the framework of the β Pic Association.
| A moving group of young stars in Carina-Vela
Accurate two-colour photometry and proper motions of 7096 young X-raystars in the ROSAT All-Sky Survey Bright Star Catalogue, version 1RXS,are extracted from the Tycho-2 Catalogue. The sample is dominated by redmain-sequence and possibly pre-main-sequence stars. On a global propermotion convergence map, two features are very prominent: the nearbysection of the Gould Belt and the Hyades convergent point. Theappearance of the Gould Belt feature with its peak at (l=244.3°,b=-12.6°) is quite similar to that of Hipparcos OB stars. When onlystars with proper motions drawing close to that point are selected,strong concentrations of stars in the direction of the Sco-Cen complexare found. Another concentration, not corresponding to any known OBassociation, is detected between the position of the Lower CentaurusCrux and Vela OB2 associations. It is a new young moving group locatedin Carina and Vela, and a near extension of the Sco-Cen complex.Contrary to the classical Gould Belt OB associations, the Carina-Velamoving group has a considerable geometric depth, the closest membersbeing as near as 30pc from the Sun. IC 2391, one of the youngest andclosest open clusters on the sky, is a part of the Carina-Vela movinggroup. The Carina-Vela moving group does not link the Sco-Cen complexwith the Vela OB associations, because the latter is much more distantthan the outer limit of the sample. It is more likely that the younglate-type population of the Scorpio-Centaurus-Carina moving groupstretches towards the Sun and possibly beyond it.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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