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Photometric discriminate for GK dwarfs of disk populations
The young and old disk populations, with ages respectively less than andgreater than about 2 x 109 yr, are separated in the (R - I,42 - 45) plane, where the 42 - 45 index of the DDO system is based onbandpasses of 75 A half-width and effective wavelengths of 4257 and 4571A. A similar, but smaller separation is seen in the (g,B2 - VI) planewhere g is the Geneva system alternative to 42 - 45 but with bandpassesof 175 A half-width and effective wavelengths of 4015 and 4476 A.Although models, based on the assumption that this separation resultsfrom a veil of weak metal lines (Magain 1983), may explain thesephenomena in the (g,B2 - VI) plane for the hotter stars, more models arerequired to test it for the DDO system and for cooler objects. Theavailable evidence suggests that an additional causation, probablyconnected with the CN abundance, also exists.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| The influence of rotation and stellar winds upon the Be phenomenon
A number of rapidly rotating B stars, not previously known as Be stars,were observed spectroscopically at H alpha. These results were thencombined with existing data to show that the spectral type of a star andthe minimum velocity at which it must rotate in order to become a Bestar are related. The trend of this relationship is found to have anatural explanation in terms of stellar winds.
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