Hostname: page-component-cd9895bd7-hc48f Total loading time: 0 Render date: 2024-12-26T03:39:53.478Z Has data issue: false hasContentIssue false
  • English
  • Français

Recent Results on Binary Cepheids

Published online by Cambridge University Press:  15 February 2018

Nancy Remage Evans
Nancy Remage Evans*
Affiliation:
Institute for Space and Terrestrial Science, York University IUE Guest Observer

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

IUE observations of hot companions of Cepheids have been used to determine the temperatures of the companions. For companions on the ZAMS, the temperatures can be used to determine the luminosity of the Cepheids from the inferred absolute magnitude of the companion. The accuracy of this method is comparable to the accuracy of calibration using Cepheids in clusters. An over-tone pulsator (SU Cas) has been identified by this technique. The luminosity of the double mode pulsator Y Car agrees with that from the PLC, confirming that is a normal Population I Cepheid. The variation of the width of the instability strip (as a function of luminosity) in the HR diagram is confirmed, and overtone and double mode pulsators are shown to be near the blue edge of the instability strip. Comparison between variables and nonvariables in the HR diagram (from IUE and cluster studies) shows very little overlap. The shape of the observed instability region may be determined both by the boundary between the variables and nonvariables and also the location of the tips of the blue loops of evolutionary tracks. Finally, eight Cepheids with hot companions which are evolved beyond the ZAMS have been studied. Half the systems are matched well by evolutionary tracks with little or no core convective overshoot near the main sequence. At least two and possibly four systems, however, cannot be matched by current isochrones.

Type
Windows on the Instability Strip
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 398 - 405
Copyright
Copyright © Cambridge University Press 1993

References

Ake, T. 1988, in “New Directions in Spectrophotometry”, eds. Philip, A. G. D., Hayes, D. S., and Adelman, S. J., (Schnectady: L. Davis Press), p. 27.Google Scholar
Antonello, E., Poretti, E. and Reduzzi, L. 1990, Astr. Ap., 236, 138.Google Scholar
Barrell, S. L. 1981, M. N. R. A. S., 196, 357.Google Scholar
Bertelli, G., Bressan, A., Chiosi, C., and Angerer, K. 1986, Astron. Ap. Suppl., 66, 191.Google Scholar
Böhm-Vitense, E. 1985, Astrophys. J., 296, 169.Google Scholar
Bohm-Vitense, E. and Proffitt, C. 1985, Astrophys. J., 296, 175.Google Scholar
Evans, N. R. 1991, Astrophys. J., 372, 597.Google Scholar
Evans, N. R.. 1992a, Astrophys. J., 389, 657.CrossRefGoogle Scholar
Evans, N. R.. 1992b, Astrophys. J., 385, 680.Google Scholar
Evans, N. R.. 1992c, preprintGoogle Scholar
Evans, N. R.. 1992d, preprintGoogle Scholar
Evans, N. R., Arellano Ferro, A., and Udalska, , 1992, Astron. J., 103, 1638.Google Scholar
Feast, M. W. and Walker, A. R. 1987, Ann. Rev. Astr. Ap, 25, 345.Google Scholar
Fernie, J. D. 1990, Astrophys. J., 354, 295.Google Scholar
Iglesias, C. A. and Rogers, F. J. 1991, Astrophys. J., 371, 408.Google Scholar
Maeder, A. and Meynet, G. 1988, Astron. Ap. Suppl., 76, 411.Google Scholar
Mateo, M., Olszewski, E. W., and Madore, B. F. 1990, in A. S. P Conf. Ser., 11, 214.Google Scholar
Meynet, G. 1992, private communication.Google Scholar
Parsons, S. B. and Ake, T. 1992, Bull. A. A. S. 24, 769.Google Scholar
Schmidt, E. G. 1984, Astrophys. J., 287, 261.Google Scholar
Stothers, R. B. and Chin, C. 1991, Astrophys. J., 381, L67.Google Scholar