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New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| 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.
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
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