Structure and Evolution of Model Helium Stars.

Abstract

view Abstract Citations (50) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Structure and Evolution of Model Helium Stars. Divine, Neil Abstract Numerical models have been constructed that describe the evolution of stars that are initially pure helium. The iterative technique, programmed for a large computer, permits the inclusion of radiation pressure, electron degeneracy, electron-scattering opacity, gravitational contraction, and detailed composition changing brought about by triple-alpha and (a, T) reactions. The twenty homogeneous (pure helium) models, which range in mass from 0.4 to 60 Mo, form a "main sequence" on the left of the H-R diagram. Evolutionary sequences of models at 0 5,1, and 6 Mo exhaust their central helium supply in times of 80,12, and 0.8 million years. Thereafter the convective core models, which have remained near their main-sequence positions, are replaced by shell-source models of increasing luminosity. At all three masses the final composition of the helium-exhausted core is almost exclusively oxygen, although a reduced rate for C22(a, )Oi6 can lead to moderate fractions of carbon. Early stages of the computed evolutionary tracks agree with other calculated sequences of fitted models. Massive helium-star models may resemble Wolf-Rayet stars in mass, luminosity, and effective temperature. Publication: The Astrophysical Journal Pub Date: October 1965 DOI: 10.1086/148356 Bibcode: 1965ApJ...142..824D full text sources ADS | data products SIMBAD (2)