SINGLE AND BINARY STAR EVOLUTION

The theory of stellar evolution, when coupled with the observed properties of stars, has taught us much about stellar interiors and about the theory itself. This review presents first: (1) a general description of the observed global properties of single stars of low, intermediate, and high mass; a description of the theoretical evolution in the Hertzsprung-Russell diagram of such stars; and an assessment of what the amalgam has taught us about the interior and surface physics of real stars; and (2) a description of the observed properties of various types of evolved close binaries; a summary of the concepts which have been found useful in constructing scenarios for the transformation of primordial binaries into evolved systems; and a judgement about what the comparison between the observations and the results of a crude theory has taught us about the physics of mass transfer within interacting binary systems and about the manner and extent of mass and angular momentum loss from these systems. The discussion then focuses on several specific topics: (1) the role of H- opacity in determining red giant surface temperatures; (2) interior composition changes due to nucleosynthesis and mixing, followed by (the first) dredge-up and changes in surface composition; (3) stellar evolution in globular clusters-mass loss on the giant branch, the horizontal and suprahorizontal branches, the primordial helium abundance, and cluster ages; (4) RR Lyrae stars in globular clusters; (5) theoretical Cepheid period-luminosity relationships and distances to Galactic and extragalactic Cepheids; (6) solar neutrino pedagogy; (7) asymptotic giant branch (AGB) stars of intermediate mass-the second dredge-up, thermal pulses, and the activation of the Ne-22 neutron source, nucleosynthesis of s-process elements in the convective shell, and the third dredge-up, which brings freshly synthesized elements to the surface; (8) AGB stars of low mass, activation of the C-13 neutron source, the production of s-process elements in the solar system distribution, the third dredge-up and the formation of carbon stars (9) termination of the AGB phase and post-AGB evolution-planetary nebula nuclei, born-again AGB stars, and self-induced novae; (10) white dwarf evolution-diffusion, nuclear burning, composition, and the age of the Galactic disk; (11) response of stars in binaries to rapid mass loss-the relationship between initial mass and the mass of the compact remnant; (12) response of white dwarfs in binary systems to mass accretion-classical and symbiotic novae, helium star cataclysmic variables; (13) scenarios for binary star evolution leading to close white dwarf pairs, some of which may merge to become subdwarf O and B stars, R CrB stars, or Type Ia supernovae; (14) star bursts, stellar mergers, and blue stragglers in clusters from the young disk to the halo. This very personal account is not intended to be comprehensive. The major aim has been to provide perspectives on a number of topics in stellar astrophysics that have interested the author over the past quarter of a century.