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Current Problems in Horizontal-Branch Theory: Some Implications for RR Lyrae Variables

Published online by Cambridge University Press:  12 April 2016

Pierre Demarque
Pierre Demarque*
Affiliation:
Yale University Observatory, New Haven, CT 06511 USA

Extract

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There are a number of good reasons for wanting to improve our understanding of the structure and evolutionary status of horizontal-branch (HB) stars. To mention a few:

  1. 1) The HB morphology of globular clusters can be used as a tool for studying the evolution of the galactic halo (Searle and Zinn 1978) and the time scale for halo collapse (Demarque 1980; Zinn 1980).

  2. 2) HB stars offer an opportunity to evaluate the helium abundance of globular clusters. This can be done either by using the R-method (Cole et al. 1983) or the width of the RR Lyrae instability strip [Deupree 1977; but see also the paper by Stellingwerf (1984) in these preceedings which casts doubt on the validity of previous calculations of the dependence of the blue edge on helium content].

  3. 3) HB stars may play an important role in understanding the integrated light of old stellar systems. In particular, blue HB stars seem to make a significant contribution to the ultraviolet light of elliptical galaxies. (Ciardullo and Demarque 1978; Gunn, Tinsley and Stryker 1981). At the same time, HB stars are believed to be the direct progenitors of asymptotic giant branch stars which have proved to be powerful tracers of stellar populations in nearby external systems (Blanco et al. 1980)

  4. 4) The RR Lyrae variables are part of the HB population. One would wish to relate the observable properties of RR Lyrae variables to their chemical compositions and ages so as to use them: a) as distance indicators for galactic globular clusters (Sandage 1982a,b) and in the Magellanic Clouds; b) as tracers of stellar populations. This has been attempted for the galactic halo and disk by Sandage (1982a,b) and for the Magellanic Clouds by Butler et al. (1982).

Type
Part IV. Population II Cepheids
Information
International Astronomical Union Colloquium , Volume 82: Cepheids: Theory and Observations , 1985 , pp. 268 - 271
Copyright
Copyright © Cambridge University Press 1985

References

Arimoto, N. 1980 Sci. Rep. Tohoku Univ., Ser. 1, 62, 134.Google Scholar
Blanco, V. M., McCarthy, M. F. and Blanco, B. M. 1980, Astrophys. J., 242, 938.CrossRefGoogle Scholar
Butler, D., Demarque, P. and Smith, H. A. 1982 Astrophys. J. 257, 592.10.1086/160015CrossRefGoogle Scholar
Caloi, V., Castellani, V., Danziger, J., Gilmozzi, R., Cannon, R. D., Hill, P. W. and Boksenberg, A. 1984 ESO Sci. Preprint No. 318.Google Scholar
Ciardullo, R. B. and Demarque, P. 1978, IAU Symp. No. 88, ed. Philip, A. G.D. and Hayes, D. S., p. 345.Google Scholar
Ciardullo, R. B. and Demarque, P. 1979, Dudley Obs. Rep. No. 14, p. 317.Google Scholar
Cole, P. W. and Demarque, P. 1984 Astrophys. J. to be published.Google Scholar
Cole, P. W., Demarque, P. and Green, E. M. 1983, ESO Workshop on Primordial Helium, ed. Shaver, P. A., Kunth, D. and Kjär, K., p. 235.Google Scholar
Corbally, C. J. 1983 Ph. D. Thesis, University of Toronto.Google Scholar
Dearborn, D. S.P., Eggleton, P. P. and Schramm, D. N. 1976 Astrophys. J. 203, 455.10.1086/154097CrossRefGoogle Scholar
Demarque, P. 1980, IAU Coll. No. 85, ed. Hesser, J. E., p. 281.Google Scholar
Demarque, P. 1981, IAU Coll. No. 68, ed. Philip, A. G.D. and Hayes, D. S., p. 301.Google Scholar
Deupree, R. G. 1977 Astrophys. J. 214, 502.CrossRefGoogle Scholar
Deupree, R. G. 1984 Astrophys. J. in press.Google Scholar
Deupree, R. G. and Cole, P. W. 1983 Astrophys. J. 269, 676.CrossRefGoogle Scholar
Dupree, A. K., Hartmann, L. and Avrett, E. H. 1984 Center for Astrophysics Preprint No. 1984.Google Scholar
Fernie, J. D. and McGonegal, R. 1983 Astrophys. J. 275, 732.Google Scholar
Freeman, K. C. and Norris, J. 1981 Ann. Rev. Astr. Ap. 19, 319.CrossRefGoogle Scholar
Gunn, J. E., Tinsley, B. M. and Stryker, L. 1981 Ap.J. 249, 48.10.1086/159259CrossRefGoogle Scholar
Harris, W. E. 1974 Astrophys. J. Letters, 192, L161.10.1086/181616CrossRefGoogle Scholar
Janes, K. A. and Demarque, P. 1983 Astrophys. J. 264, 206.CrossRefGoogle Scholar
King, C. R., Da Costa, G. S. and Demarque, P. 1984 Astrophys. J. to be published.Google Scholar
Mould, J. R., Da Costa, G. S. and Crawford, M. D. 1984 Astrophys. J. in press.Google Scholar
Peterson, R. C. 1983, Astrophys. J. 275, 737.CrossRefGoogle Scholar
Renzini, A. 1983, Mem. Soc. Astr. Italiana, 54, 335.Google Scholar
Rich, R. M., Mould, J. R. and Da Costa, G. S. 1984, IAU Symp. No. 108, ed. van den Bergh, S. and de Boer, K. S., p. 45.Google Scholar
Robertson, J. W. and Faulkner, D. J. 1972 Astrophys. J. 171, 309.10.1086/151283CrossRefGoogle Scholar
Sandage, A. 1982a, Astrophys. J. 252, 553.CrossRefGoogle Scholar
Sandage, A. 1982b, Astrophys. J. 252, 574.CrossRefGoogle Scholar
Schommer, R. A., Olszewski, E. W. and Aaronson, M. 1984 preprint.Google Scholar
Searle, L. and Zinn, R. 1978 Astrophys. J. 225, 357.10.1086/156499CrossRefGoogle Scholar
Stellingwerf, R. F. 1984 These Proceedings.Google Scholar
Sweigart, A. V. and Gross, P. C. 1976 Astrophys. Suppl., 32, 367.10.1086/190401CrossRefGoogle Scholar
Sweigart, A. V., Mengel, J. G. and Demarque, P. 1974 Astr. Ap. 30, 13.Google Scholar
Taam, R. E., Kraft, R. P. and Suntzeff, N. 1976 Astrophys. J., 207, 201.10.1086/154485CrossRefGoogle Scholar
VandenBerg, D. A. 1983 Astrophys. J. Suppl. 51, 29.10.1086/190839CrossRefGoogle Scholar
VandenBerg, D. A. and Bridges, T. R. 1984 Astrophys. J. 278, 679.CrossRefGoogle Scholar
Zinn, R. 1980 Astrophys. J. Suppl. 42, 19.10.1086/190643CrossRefGoogle Scholar