Publication Abstracts

Carson and Stothers 1976

Carson, T.R., and R. Stothers, 1976: Evolutionary problems of Cepheids and other giants investigated with new radiative opacities. Astrophys. J., 204, 461-471, doi:10.1086/154190.

New evolutionary tracks, pulsation constants, and pulsational stability coefficients have been calculated for stellar models applicable to the problems of classical Cepheids, by adopting (a) the standard Cox-Stewart opacities and (b) the new Carson opacities. The theoretical mass-luminosity relation is slightly fainter for the new opacities, but neither this decrease of luminosity nor the somewhat greater duration of the "blue loop" during core helium burning can be discriminated on the H-R diagram by the use of present observational data for giant stars in moderately young clusters of the Galaxy and the Magellanic Clouds. The masses of Cepheids inferred from the pulsation constants and from the pulsational period ratios are significantly smaller than the masses inferred from evolutionary theory, for both sets of opacities, but the masses that can be inferred from the secondary bump on the radial-velocity curve are now predicted to agree with the evolutionary masses if the new opacities are used. In contrast to the older opacities, the new opacities lead to revised pulsational instability results that are in good agreement with observations: thus, convection in the hotter envelopes is much less important than before, so that the phase lag between luminosity and radial velocity at the stellar surface is closer to 90°; and the blue edge of the theoretical instability strip on the H-R diagram is significantly bluer than before, although it may now have too steep a slope and the problem of the theoretically unlimited red edge remains. Nevertheless, the present improvements are achieved with a normal helium abundance, no mass loss, and a conventional treatment of convection. The predicted transition between second-overtone instability and fundamental-mode instability agrees excellently with the well-observed transition in the Small Magellanic Cloud. Axial rotation is found to increase the effective temperature of the theoretical blue edges by a very slight amount.

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BibTeX Citation

  author={Carson, T. R. and Stothers, R.},
  title={Evolutionary problems of Cepheids and other giants investigated with new radiative opacities},
  journal={Astrophys. J.},

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RIS Citation

ID  - ca09710b
AU  - Carson, T. R.
AU  - Stothers, R.
PY  - 1976
TI  - Evolutionary problems of Cepheids and other giants investigated with new radiative opacities
JA  - Astrophys. J.
VL  - 204
SP  - 461
EP  - 471
DO  - 10.1086/154190
ER  -

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