Upper Main Sequence Stars with Anomalous Abundances

This volume contains papers presented at IAU Colloquium No. 90. at the Crimean Astrophysical Observatory in May of 1985. A few additional contributions are included from authors who for various reasons were unable to attend the meeting. Four years have passed since the last major international conference on chemically peculiar stars of the upper main sequence was held in Liege. Belgium in 1981. Previous conferences were held in 1975 (Vienna. Austria) and in 1965 (Greenbelt. Maryland. USA). As the proceedings of this Colloquium show. the recent availability of ultraviolet spectra of large numbers of normal and chemically peculiar A and B stars is having a major impact on the way we study these objects. and has led to many new. exciting and unanticipated results. Simultaneously. the more traditional study of optical spectra has been advanced through the increasing use of very high spectral resolution with high signal-to-noise detectors. The chemically peculiar (CP) stars on the upper main sequence belong in the standard framework within which we understand stellar evolution and the history of matter. Recent work has made it clear that the unusual chemistry and magnetic structure of these objects is of relevance across the broad domain of stellar astronomy. from the upper main sequence to horizontal branch stars and white dwarfs. Metal poor (J>. Boo) as well as metal rich (Ap. Am) stars are an integral part of the picture.

Inhalt

Section I - Theoretical Considerations.- The Origin and Structure of the Magnetic Fields of the Chemically Peculiar Stars [Invited Review].- Origin of the Magnetic Field [Invited Review].- On the Spottedness, Magnetism and Internal Structure of Stars.- Investigations of the Magnetic Fields of Chemically Peculiar Stars of Different Age.- The Magnetic Field and Other Parameters of the Chemically Peculiar Stars.- On the Perturbation Technique for the Influence of Magnetic Field on Stellar Oscillations.- On the Magnetic Field of ? CrB.- Estimation of Stellar Surface Magnetic Fields by the Curve-of -Growth Method:.- Discussion.- Does ? Cep Indicate a Non-axisymmetric Dynamo?.- Model Atmospheres and Radiative Transfer in Chemically Peculiar Stars: Interpretational Significance of Non-LTE [Invited Review].- Discussion: Hubený.- Influence of the Magnetic Field on the Polarization of Radiation Scattered by Electrons in Stellar Atmospheres and Envelopes.- A Determination of Magnetic Fields of T Tau and Ae/Be Herbig Stars Using the Parameters of their Linear Polarization.- Practical Problems in the Analysis of CP Stars [Invited Review].- Missing Levels and Lines of Astrophysical Importance:.- Combined Discussion: Cowley and Johansson - Johansson and Cowley.- Characteristic Absorption Features in the Spectra of Ap -Si Stars Between 1250 and 1850 ft Å.- Space Observations of Chemically Peculiar and Related Normal Stars [Invited Review] :.- Combined Discussion: Artru and Lanz - Leckrone.- Study of Inhomogeneities on the Surface of Magnetic CP Stars [Invited Review].- Khokhlova.- Inverse Problems in Astrophysics.- The Distribution of Fe, Cr, and Si over the Surface of ? Aur.- Application of Deutsch's Method for 53 Cam.- The Nonhomogeneous Distribution of Abundances and the Magnetic Field Measurements in CP Stars.- Section II - Systematics, Photometry.- Systematics of CP Stars [Invited Review].- Spectroscopy of CP Stars in the Groups of Different Age:.- Combined Discussion: Hensberge and Van Rensbergen - Klochkova and Kopylov.- Rotation, Variability and Age of Ap Stars.- Light Curve Analysis of Rotating Variable Stars:.- A Search for Long-Term Photometric Variability in CP2-Stars:.- The Nature of Balmer Line Variability in Chemically Peculiar Stars:.- The Variability of the ?5200 Feature in CP2 Stars.- Short Time Light Variations of Ap-Stars.- CP-Stars in the Near Infrared: Normal.- H? and OI Photometry of Upper Main Sequence Stars with Anomalous Abundances.- A Photometric Investigation of the Magnetic Star 53 Camelopardalis.- Spectrophotometry of the Broad Continuum Features in Magnetic Ap Stars.- On the Duplicity of CP3 Stars.- Investigations of CP and Normal Stars With Coadded Dominion Astrophysical Observatory Spectrograms.- Rapid Oscillations of CP2-Stars [Invited Review].- Discussion: Weiss.- Computed Spectral Line Variations for Oblique Nonradial Pulsators.- Short-Periodic Radial Velocity Variations of the B9p Star ET And.- Frequency Analysis of the Rapidly Oscillating Ap Star HD 60435.- Investigations of the Magnetic Star 53 Cam Variations Using the Spectra of High Time Resolution.- HD 24975: A New Delta Scuti Star? (or a Mild Ap Star with Short Photometric Variations?).- Section III - Magnetic CP Stars.- Hot Magnetic Stars: Abundances, Spectroscopy, Photometry, Systematics [Invited Review].- On the Ultraviolet Photometric Variability of the Helium-Weak B Stars (from ANS Data).- Intermediate Peculiar Stars: The Bp-ApSiStars [Invited Review):.- Combined Discussion: Zelwanowa and Schöneich - Mégessier.- Blanketing Hypothesis and Light Variations of HD 27309.- A Spectroscopic Study of the Bp-Star ? Aur.- The Ultraviolet Spectral Energy Distribution of the Magnetic Ap Star HD 170000 Inside and Outside of the Spots.- Cool Magnetic CP Stars [Invited Review].- Discussion: Adelman and Cowley.- Abundance Analysis of Three Ap Stars: HD 2453, HD 8441, and HD 192913.- Absorption Lines of Ca II and H in the Near IR Region of the Magnetic Star HD 152107.- A Search for Heavy Elements in the Ultraviolet Spectra of Ap Stars.- The Investigations of Variations in the Depression >.4200, A5200 of the Magnetic Stars 53 Cam and Beta CrB.:.- Discussion.- The Age of ? UMa.- Line Spectrum Variations in the Ap Star HD 51418.- ? CrB - a Rosetta Stone?.- Some Structural Features of Magnetic Fields of the Chemically Peculiar Stars ? CrB and ?2 CVn.- ? Lyrae - A Binary System with Anomalous Abundances and Magnetic Field.- Section IV - Non-Magnetic CP and Related Stars.- Spectroscopic Analyses of Hot Main Sequence Stars [Invited Review].- Diffusion Processes and Chemical Peculiarities in Magnetic Stars [Invited Review]:.- Combined Discussion: Sadakane - Alecian.- Chemical and Temperature Inhomogeneities on Stellar Surfaces as a Result of an Instability.- Non-Magnetic Intermediate-Temperature Stars: A Review [Invited Review].- Discussion: Dworetsky.- The Abundance of Gallium in B-type Chemically Peculiar Stars.- Gallium Overabundance in the Ap-Si Star HD 25823.- The Most Iron-Deficient Manganese Star HR 562.- The Light and Spectrum Variable CP2 Star HR 6127.- The Analysis of Chemical Composition of Am Star Atmospheres [Invited Review].- Discussion: Boyarchuk and Savanov.- Lithium in Am and ? Del Stars.- The Li I 6708 Feature in CP Stars.- The Metallic-Lined Star 32 Aquarii.- Particle Transport in Non-Magnetic Stars [Invited Review].- The Planetoid-Impact Hypothesis of CP, F, A, and B Star Formation: Possibilities and Perspectives:.- Combined Discussion: Michaud - Drobyshevski.- General Index.