Astron. Astrophys. 326, 620-628 (1997)

Multiwavelength studies of    Cephei stars:  Ceti

H. Cugier and D. Nowak

¹ Astronomical Institute of the Wroclaw University, ul. Kopernika 11, PL-51622 Wroclaw, Poland

Received 22 April 1996 / Accepted 21 March 1997

Abstract

We discuss diagnostic aspects that follow from identification of the driving mechanism for the pulsation of  Cephei stars by an analysis of the well-observed star  Ceti. Ground-based photometric and ultraviolet IUE spectro-photometric observations were used. We find that the stellar model which fits the observed frequency of oscillation and nonadiabatic observables (amplitude ratios and phase differences of the multicolour photometric measurements) describes also very well the energy flux distribution and spectral line profiles. Stellar models calculated for OPAL opacities with fit the observations best.

We find that  Ceti is a star pulsating in the first overtone ( ) of the radial (l = 0) mode. The luminosity of this star is in the range of 4.04 log 4.16 and mass . We also discuss how these parameters can be improved using nonadiabatic observables.

Key words: fi Cephei starsstars: oscillationsstars: early-typestars: atmospherestars: variable: other

Send offprint requests to: H. Cugier

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Contents

• 1. Introduction
• 2. Oscillation parameters
  • 2.1. Period
  • 2.2. Nonadiabatic observables
• 3. Mean stellar parameters
• 4. IUE observations
• 5. Analysis of the continuum flux distribution
• 6. Analysis of line profiles
  • 6.1. Mean spectrum of  Cet
  • 6.2. Line profile behaviour during pulsation cycle
• 7. Luminosity, mass and age
• 8. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: October 15, 1997
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