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Time Dependent Convection and the Pulsations of Polaris

Published online by Cambridge University Press:  15 February 2018

Siobahn M. Morgan  and
Arthur N. Cox
Siobahn M. Morgan
Affiliation:
University of Northern Iowa, U. S. A.
Arthur N. Cox
Affiliation:
Los Alamos National Laboratory, U. S. A.

Extract

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The low amplitude radially pulsating classical Cepheid Polaris (α UMi) has well observed decreasing radial velocity and light amplitudes and an increasing period. Recent work indicates that Polaris may stop pulsating by 1995 (Dinshaw et al, 1989), which would make it an excellent indicator for the red edge of the Cepheid instability strip in the Hertzsprung-Russell diagram.

We have calculated Population I envelope models with 200 mass shells of a 5.5 M⊙ star near Teff = 5700 K and log(L/L⊙) = 3.11 which match Polaris’ characteristics (Arellano Ferro, 1984). Models were calculated using the Linear Non Adiabatic pulsation analysis code of Castor (1971). The effects of convection on the pulsational stability were calculated with the time dependent convection theory of Cox, Brownlee and Eilers (1966) as discussed by Cox and Guili (1968). The characteristics of the models were altered until the appropriate period, temperature and luminosity were obtained.

Type
Theoretical Breakthroughs
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 308
Copyright
Copyright © Cambridge University Press 1993

References

Arellano Ferro, A. 1984, M. N. R. A. S., 209, 481.Google Scholar
Castor, J. I. 1971, Astrophys. J., 166, 109.Google Scholar
Cox, A. N., Brownlee, R. R. and Eilers, D. D. 1966, Astrophys. J. 144, 1024.Google Scholar
Cox, J. P. and Giuli, R. T. 1968, Principles of Stellar Structure, Gordon and Breach, New York, p. 1045.Google Scholar
Dinshaw, N., Matthews, J. M., Walker, G. A. H., and Hill, G. M. 1989, Astronom. J., 98, 2249.Google Scholar
Morgan, S. M. 1992, these proceedings. Google Scholar