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The Cepheid Instability “Wedge“

Published online by Cambridge University Press:  15 February 2018

Siobahn M. Morgan
Siobahn M. Morgan*
Affiliation:
University of Northern Iowa, U. S. A.

Extract

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For the most part it had been assumed that the red and the blue edges of the Cepheid Instability region were parallel. However, previous work by Pel and Lub (1978) and recent work by Fernie (1990) seems to reveal a rather interesting structure to the shape of the Cepheid Instability region. Figure 1 shows the shape defined using the data from Fernie (1990) and the observational data of Gieren (1989). It is apparent that the edges defined by the distribution of these points are not parallel.

I have calculated a series of pulsation models that included varying values of the mixing length to try and produce a distribution of Cepheids as seen in Figure 1. Calculations were done using the methods outlined by Castor (1971) with a Linear Non Adiabatic pulsation code to determine the characteristics for a given model.

Type
Theoretical Breakthroughs
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 307
Copyright
Copyright © Cambridge University Press 1993

References

Castor, J. I. 1971, Astrophys. J., 166, 109.Google Scholar
Fernie, J. D. 1990, Astrophys. J., 354, 295.Google Scholar
Gieren, W. P. 1989, Astron. Astrophys., 225, 381.Google Scholar
Pel, J. W. and Lub, J. 1978, in The HR Diagram, IAU Syrup, number 80, eds. Davis Philip, A. G. and Hayes, D. S., Reidel, Dordrecht Holland, p. 229.Google Scholar