THE STR OMVIL SEVEN-COLOUR PHOTOMETRIC SYSTEM FOR GAIA CLASSIFICATION OF PECULIAR STARS.pdf

761 THE STROMVIL SEVEN-COLOUR PHOTOMETRIC SYSTEM FOR GAIA:CLASSIFICATION OF PECULIAR STARSV. Straizys1, E. Hg2, A.G. Davis Philip31 Institute of Theoretical Physics and Astronomy, Gostauto 12, Vilnius 2600, Lithuania2 Copenhagen University Observatory, Juliane Maries Vej 30, 2100 Copenhagen , Denmark3 Institute for Space Observations and Union College, Schenectady, NY 12308, U.S.A.ABSTRACTIn our previous publications it was shown that theStromvil seven-colour photometric system, when setup on a GAIA-type satellite, will be able to clas-sify stars of all normal spectral classes down to 16mag. In the present paper we demonstrate that thesame system makes possible the photometric identi-cation of a number of peculiar types of stars, includ-ing emission-line stars, metallic-line A and F stars,chemically peculiar B and A stars, metal-decient F{G{K dwarfs (subdwarfs), metal-decient G and K gi-ants, blue horizontal-branch stars, white dwarfs andcarbon-rich stars.Key words: space photometry; stellar classication;GAIA satellite.1. INTRODUCTIONStraizys, Crawford and Philip (1996) have shownthat if the Stromgren four-colour system is supple-mented by three passbands of the Vilnius system at374, 516 and 656 nm, the combined Stromvil sys-tem becomes capable of classifying stars in spectralclasses (or eective temperatures) and luminosities(or gravities) everywhere in the HR diagram, evenwhen interstellar reddening is present. Setting up theStromvil system on a GAIA-type satellite makes pos-sible the classication of tens of millions stars downto 16 mag (Straizys Hg 1995). Among them, upto 10 per cent of stars will be either metal-decientor will have other peculiarities in their spectra. Itis important to have a photometric method for iden-tifying these peculiar stars and for estimating theirmatallicity or degree of peculiarity.2. PHOTOMETRIC CLASSIFICATION IN THEVILNIUS SYSTEMThe possibility of identifying various types of pecu-liar stars has been demonstrated