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Structure and evolution of model helium stars

Citation

Divine, Theodore Neil (1965) Structure and evolution of model helium stars. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05162003-095204

Abstract

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Numerical models have been constructed which describe the evolution of stars which are initially pure helium. The iterative technique, programed 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 ([alpha],[gamma]) reactions.

The twenty homogeneous (pure helium) models, which range in mass from 0.4 to 60M[...] form a "main sequence" on the left of the H-R diagram. Evolutionary sequences of models at 0.5, 1, and 6M[...] exhaust their central helium supply in times of 80, 12, and 0.8 million years. Thereafter the connective 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 C[superscript 12]([alpha],[gamma])0[superscript 16] can lead to moderate fractions of carbon.

There is no clear indication that the models correspond to any group of observed stars. Massive helium star models may resemble Wolf-Rayet stars in mass, luminosity, and effective temperature.

Item Type:Thesis (Dissertation (Ph.D.))
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Oke, J. Beverley
Thesis Committee:
  • Unknown, Unknown
Defense Date:5 November 1964
Record Number:CaltechETD:etd-05162003-095204
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05162003-095204
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:1831
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:16 May 2003
Last Modified:26 Dec 2012 02:42

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