No part of the Hertzsprung-Russell diagram shows a more pronounced diversity of stellar types than the upper part, which contains the most luminous stars. Can one visualize a larger difference than between a luminous, young and extremely hot Of star, and a cool, evolved pulsating giant of the Mira type, or an S-type supergiant, or - again at the other side of the diagram - the compact nucleus of a planetary nebula? But there is order and unity in this apparent disorder! Virtually all types of bright stars are evolutionally related, in one way or the other. Evolution links bright stars. In many cases the evolution is speeded up by, or at least intimately related to various signs of stellar instability. Bright stars lose mass, either continuously or in dramatic sudden events, they vibrate or pulsate - and with these tenuous, gigantic objects this often happens in a most bizarre fashion. Sometimes the evolution goes so fast that fundamental changes are observable in the time span of a human's life - several of such cases have now been identified.

Inhalt

1: The Upper Boundaries of the Hertzsprung-Russell Diagram.- 1.1. Preamble.- 1.2. The Most Luminous Stars.- 1.3. Gravitational Acceleration Versus Radiation Forces.- 1.4. Inclusion of the Mass-Luminosity Relation.- 1.5. The Effective Value of the Acceleration of Gravity; Influence of Radiation Pressure.- 1.6. Influence of Rotation and of Turbulent Motions.- 1.7. 'Boundaries' to the Hertzsprung-Russell Diagram.- 1.8. Terminology Related to Extended Atmospheres.- 2: The Main Observational Characteristics of the Most Luminous Stars.- 2.1. Spectral and Luminosity Classification.- 2.2. Absolute Magnitude and Luminosity Criteria.- 2.3. The Effective Temperature Scale and the Bolometric Correction.- 2.4. Masses of Massive Stars.- 2.5. Radii of Luminous Stars.- 2.6. geff-Values in Extreme Objects.- 2.7. The Distribution of Light over the Surface of Supergiants.- 2.8. Magnetic Fields of Luminous Stars.- 2.9. Turbulent Velocities.- 2.10. Rotational Velocities in Atmospheres of Bright Stars.- 2.11. Polarization of Light of Stars with Extended Atmospheres.- 3: Spectral Characteristics and Stellar Parameters for the Main Groups of Luminous Stars; Some Prototypes.- 3.1. O- and Bright B-Stars.- 3.2. The Of and Oef Stars.- 3.3. The Most Luminous Galactic Star.- 3.4. The Wolf-Rayet Stars.- 3.5. The P Cygni Stars, and P Cygni Profiles.- 3.6. The Oe, Be-, and Shell-Type Stars.- 3.7. The CNO-Stars (or: OBCN Stars).- 3.8. The Super-Supergiants (Hypergiants).- 3.9. The Most Luminous Extragalactic Star..- 3.10. G- and K-Type Supergiants; Zeta Aurigae Stars.- 3.11. The Coolest of the Bright Stars.- 3.12. The Central Stars of Planetary Nebulae.- 4: The Evolution of Massive Stars.- 4.1. The First Phases of the Evolution of Massive Stars.- 4.2. The Main Sequence; Life Times, Stability.- 4.3. Post-Main-Sequence Evolution of Massive Stars.- 4.4. Convection and Semi-Convection.- 4.5. The Influence of Mass-Loss on the Evolution of Massive Stars.- 4.6. Stellar Abundances and Nuclear Reactions; the Influence of Thermal Pulses.- 4.7. The Mira Stars.- 4.8. The Carbon Burning and Later Phases.- 4.9. Supernovae.- 4.10. Evolution of Close Massive Binaries.- 4.10.1. The Roche Surface.- 4.10.2. Evolution of Close Binary Stars; the Conservative Case.- 4.10.3. Evolution of Close Binaries in the Non-Conservative Case.- 4.10.4. The Last Phases of Binary Star Evolution.- 4.11. The Origin of Wolf-Rayet Stars.- 4.12. The Origin of X-Ray Binaries; Mass Transfer onto a Compact Companion.- 4.13. Stellar Rotation and Evolution.- 5: The Structure of Very Tenuous Stellar Atmospheres.- 5.1. Atmospheric Models; Radiative or Convective Equilibrium.- 5.2. The Assumption of Plane-Parallel Atmospheric Layers.- 5.3. Models of Very Tenuous Atmospheres; the Plane-Parallel Case.- 5.4. Models of Extended and Spherical Stellar Atmospheres; the Static Case.- 5.5. Expanding Spherical Stellar Atmospheres; Introduction.- 5.6. The Radiation Force on Outer Stellar Layers.- 5.7. Radiation-Driven Expanding Atmospheres; the Subsonic Region.- 5.8. Line-Driven Stellar Winds.- 5.9. Model Envelopes of Early-Type Stars with Line-Driven Stellar Winds.- 5.10. Convection in Supergiant Atmospheres.- 6: Chromospheres, Coronae, Gas and Dust Around Luminous Stars.- 6.0. Generalities.- 6.1. What is a Stellar 'Chromosphere'?.- 6.2. Conditions for the Occurrence of Emission Lines; Chromospheric Indicators.- 6.3. Observations in Some Chromospheric Indicators.- 6.4. Properties of Chromospheres and 'Warm Envelopes' in Various Types of Stars as Derived from Spectral Investigations.- 6.5. Outward Increase of the Source Function or the Temperature in Near-Photospheric Layers.- 6.6. Chromospheric and Coronal Heating - the Solar Case.- 6.7. Wave Modes in a Stellar Photosphere.- 6.8. The Generation of Mechanical Fluxes in Stellar Photospheres.- 6.9. Comparison of Predicted and 'Observed' Stellar Mechanical Fluxes.- 6.10. The Computation of Stellar Coronal Parameters.- 6.10.1. Historical and General Remarks.- 6.10.2. The Non-Magnetic Approach.- 6.10.3. The Role of Magnetic Fields in Coronal Heating.- 6.11. The Observation of Coronae of Luminous Stars.- 6.12. Circumstellar Gas - (a) Circumstellar Spectral Lines.- 6.13. Circumstellar Gas - (b) Thermal Microwave and Infrared Emission from Bright Stars.- 6.14. Circumstellar Gas - (c) Maser Effects.- 6.15. Circumstellar Dust.- 6.16. Circumstellar Gas and Dust: the Red Supergiant VY CMa.- 6.17. Circumstellar Gas and Dust: the Object ? Carinae.- 7: Mass-Loss from Bright Stars.- 7.1. Outline.- 7.2. Observational Indicators and General Properties of Mass-Flow.- 7.3. The Expected Shape of Spectral Lines in an Expanding Atmosphere; Some Well-Studied Cases.- 7.4. Summary of Observationally-Determined Values for Mass-Loss.- ? Carinae.- P Cygni.- Wolf-Rayet Stars.- O- and Bright B-Type Stars.- A-Type Supergiants.- F-, G-, K-Type Supergiants.- Late-Type Giants and Supergiants.- Summary of Mass Flux Data; Comprehensive Representations.- 7.5. Stellar Mass-Flux Theory Based on Fluctuation Theory.- 7.6. The Mechanisms of Supergiant Mass-Loss.- 7.7. Expanding Dust Shells.- 8: Variability of Supergiant Atmospheres.- 8.1. Introduction; History.- 8.2. Brightness Variations.- 8.3. Colour Variability.- 8.4. Spectrum Variations.- 8.5. Variability of Stellar Winds.- 8.6. Supergiant Atmospheric Pulsations.- 8.7. Causes of Long-Period Variability.- 9: Stars of Transient Extreme Brightness; Novae, Supernovae.- 9.1. Introduction.- 9.2. Types, Light-Curves, and Absolute Magnitudes.- 9.3. Pre- and Post-Novae; Novae as binaries; are Classical Novae Recurrent?.- 9.4. The Main Observational Parameters of Novae.- 9.5. Line Spectra; Description and Analysis; Abundances; 'Coronal' lines; X-Ray Emission and X-Ray Novae.- 9.6. The Continuous Spectra; Dust Shells.- 9.7. Rapid Brightness Fluctuations of Novae.- 9.8. Morphology of Novae Envelopes and Surrounding Nebulosities.- 9.9. Theories and Models on the Development of the Photospheres of Novae.- 9.10. The Origin of the Nova Instability.- 9.11. Supernovae; Types, Lightcurves, and Energies.- 9.12. The Continuous Spectra of Supernovae.- 9.13. Line Spectra of Type I Supernovae.- 9.14. Structural and Dynamical Models of Type I Supernovae.- 9.15. Type II Supernovae; Line Spectra, Light Curves, Scenario of Events.- 9.16. High Energy Photon and Particle Emissions from Supernovae.- 9.17. Supernova Remnants.- 9.18. Supernova Remnants in the Large Magellanic Cloud.- 9.19. The Interaction of Supernova Ejecta with the Interstellar Medium.- References.- Symbols and Notations.- Alphabetic List of Stars.- Objects by Name.- Supernovae (By Year of Appearance).