The Early Type Stars

I/An Introduction to the Early Type Stars and to the Means of Observing Them.- 1 The early type stars.- 2 Techniques by which information is obtained.- 3 Stellar spectrographs.- 4 The classification and description of early type spectra.- II/Improved Systems of Spectral Classification.- 1 Systems depending upon the visual inspection of spectrograms.- 1.1 The Victoria Revised system.- 1.2 The MKK system.- 1.3 The MK system.- 2 Systems depending upon measured quantities.- 2.1 The work of E. G. Williams.- 2.2 The work of P. Rudnick.- 2.3 The work at the Dominion Astrophysical Observatory.- 2.4 The work at the Royal Observatory, Edinburgh.- 2.5 The work of Barbier, Chalonge, and Divan.- 2.6 The work at the Crimea Observatory.- 2.7 The work at the Stockholm Observatory.- III/The Luminosities of the O and B Type Stars.- 1 General principles of calibrating luminosity criteria.- 2 The calibration of the Victoria system of luminosity determination.- 2.1 The A and B type stars.- 2.2 The O type stars.- 3 Tests of the Victoria system.- 4 The calibration of the MK luminosity classes for B type stars.- 5 The absolute magnitudes of the B type supergiants.- 6 A comparison of Victoria and MK absolute magnitudes for B type stars.- IV/Spectral Studies by Means of Photometry.- 1 Spectral classification and the UBV system of photometry.- 1.1 The Q method of spectral classification.- 1.2 The work of Wesselink on stars in the Magellanic Clouds.- 2 Classification by means of narrow-band filters.- 3 Narrow-band photometry by interference techniques.- 4 Observations of OB stars from space vehicles.- 5 The classification problem.- V/Interstellar Material and the OB Stars.- 1 The observation of selective extinction.- 2 The diffuse interstellar absorption features.- 3 The sharp interstellar lines.- 4 Interstellar polarisation.- VI/The Distribution of O and B Stars.- 1 The general distribution of early type stars.- 2 Comprehensive lists of O and B stars.- 3 Some important groups of O and B stars.- 3.1 The Pleiades.- 3.2 The Orion association.- 3.3 The Scorpio-Centaurus association.- 3.4 The Cassiopeia-Taurus group.- 3.5 The ? Persei association.- 3.6 The h and ? Persei association.- 3.7 The I Lacertae association.- 3.8 NGC 2264.- 3.9 NGC 3293 and NGC 4755.- 3.10 Regions of origin of O and B stars.- VII/The Helium Spectrum.- 1 Spectroscopic notation and the energy level diagram of helium.- 2 Stark broadening and the forbidden lines.- 3 Non-equilibrium effects due to the presence of metastable levels.- 3.1 Effects due to the metastability of the 21S and 23S levels of Hei.- 3.2 Effects in other spectra of the same structure.- VIII/Wave-length Studies of Early Type Stars.- 1 Measurements for wave length.- 2 Standard wave lengths.- 3 The refractivity of air.- 4 The correction of measured wave lengths to absolute values.- 5 Wave-length and identification lists for O and B stars.- 6 Radial-velocity studies.- 6.1 The selection of wave lengths for radial-velocity work.- 6.2 Catalogues of radial velocities of O and B stars.- 6.3 The probable errors of stellar radial velocities.- 7 Motions of the OB stars.- IX/Spectroscopic Binaries.- 1 Motion in an ellipse and the derivation of an orbit.- 2 Catalogues of spectroscopic and eclipsing binaries.- 3 The secular variation of orbital elements.- 4 The falsification of velocity curves.- 5 Estimates of the masses of the early type stars.- 6 The observed mass-luminosity law.- X/Spectrophotometric Techniques.- 1 Photographic spectrophotometry.- 1.1 Intensity calibrations.- 1.2 Methods of reducing microphotometer tracings.- 1.3 Standard equivalent widths and line profiles.- 2 Photoelectric scanning of spectral lines.- 3 Correction for the instrumental profile.- XI/The Interpretation of Normal Main-Sequence Early Type Spectra.- 1 The problem.- 2 Methods of analysis developed at Kiel and the results.- 2.1 Coarse analysis.- 2.2 Fine analysis.- 3 Methods of analysis developed at Michigan and the results.- 4 Methods of analysis developed at Victoria and the results.- 5 The helium abundance.- 6 Other model atmosphere studies of early type stars.- XII/Apparently Unusual Abundances in Early Type Stars.- 1 The helium stars.- 2 Stars with strong lines of Pii and Piii.- 3 The star ? Sculptoris.- 4 B stars in the galactic halo.- XIII/The Wolf-Rayet Stars.- 1 Introduction.- 1.1 General characteristics of Wolf-Rayet stars.- 1.2 The spectral classification of Wolf-Rayet stars.- 1.3 The number of Wolf-Rayet stars known and their distribution.- 2 The properties of the Wolf-Rayet stars.- 2.1 Absolute magnitudes and colours.- 2.2 Masses.- 2.3 Radii.- 2.4 Temperatures.- 2.5 Variability.- 3 The interpretation of Wolf-Rayet spectra.- 3.1 The interpretation of the emission line spectrum.- 3.2 The spectrum from the expanding shell.- 4 Wolf-Rayet binaries.- 5 Some unsolved problems raised by Wolf-Rayet stars.- XIV/Supergiants and P Cygni.- 1 The early type supergiants.- 2 The variability of supergiants.- 3 The interpretation of the spectra of supergiants.- 4 P Cygni.- XV/Be stars, Shell stars, and Of stars.- 1 Stellar rotation and the Be stars.- 2 The Be stars.- 3 Shell stars.- 3.1 The spectrum of ? Tauri.- 3.2 The spectrum of 48 Librae.- 4 The Of stars.- XVI/The Beta Canis Majoris Stars.- 1 Introduction.- 2 Generalisations.- 2.1 The period-luminosity relation.- 2.2 Phase relationships and line shifts.- 2.3 Rotation.- 2.4 Emission lines.- 3 Observations of individual stars.- 4 Theoretical interpretation of the ? Canis Majoris stars.- 5 Stars related to the ? Canis Majoris stars.- Appendix/The Basis of the Theory of Normal Stellar Spectra.- References.- Index of Stars Mentioned in the Text.- Index of Subjects.