The European Network of Laboratories: Visual Double Stars

Abstract

The study of double stars has since long been recognized as a basic key to the understanding of star formation and stellar evolution. Moreover, close visual double stars have always been systematically neglected in photometric observational programmes although they contain an important part of physically associated systems. It is then timely to organize major observational programmes of these objects for a number of good reasons:1.The frequency of double stars is continuously reviewed and the rate of their detection is steadily increasing — both from ground–based and space observations — in such a way that they no longer can be discarded in any models of galactic structure;2.Space observations (HIPPARCOS, HST) significantly improve the quality and the importance of stellar samples and permit to better take into account some of the selection effects;3.The high–quality astrometric (and also photometric) data that will be provided for such systems by the space observations should be matched with accurate and homogeneous complementary astrophysical information such as colour indices and spectral classification. Such information for close visual double stars is unfortunately almost non-existent but are now being more easily accessible with the use of CCD detectors.

CCD photometry and astrometry of visual double and multiple stars of the HIPPARCOS Catalogue

“…Already in August 1990 a European Network of Laboratories "Visual Double Stars" was founded (Oblak et al 1992a) for combining the efforts of scientist in six European countries with the goal to achieve accurate ground-based photometric and astrometric data of visual double and multiple stars as a complement to HIPPARCOS space observations (Oblak & Lampens 1992).…”

“…1 Tables 1 to 4 are only available in electronic form at the CDS via ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html stars in the southern hemisphere (Oblak et al 1992b). Short summaries of the observations at ESO La Silla have been given by Lampens et al (1997) and Oblak et al (1997).…”

Observational Programme for Classical and CCD Photometry of Visual Double and Multiple Systems

“…The observational programme, started in the context of the European Network of Laboratories "Visual Double Stars" (Oblak et al 1992), is therefore based on samples extracted from the "Catalogue des Composantes d'Etoiles Doubles et Multiples" (CCDM, Dommanget, 1989) and reported in Annex 1 (Double and Multiple Systems) of the HIPPARCOS Input Catalogue (C. Turon et al 1992).…”