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

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1. Introduction

Recent stability surveys for stellar models corresponding to [FORMULA]  Cephei stars performed by Dziembowski & Pamyatnykh (1993) and Gautschy & Saio (1993) leave no doubt that the [FORMULA] -mechanism is responsible for the origin of pulsation of these objects. An important property of [FORMULA]  Cephei-type oscillations is that their amplitudes are small and the linear approximation can be used. The basic aspects of such a theory are well elaborated for early-type stars, cf. Dziembowski (1994, 1995).

Cugier, Dziembowski & Pamyatnykh (1994) compared predictions of the linear nonadiabatic theory for amplitude ratios and phase differences - the nonadiabatic observables - with multicolour photometry and radial velocity data of [FORMULA]  Cephei stars. The agreement is satisfactory and, in most cases, the harmonic degree l of oscillations can be determined. In particular, [FORMULA]  Cet is a star pulsating in the radial mode, l = 0. Furthermore, two-colour photometry of [FORMULA]  Cep stars can be used to discriminate between different opacity data for modelling the internal structure of these stars, cf. Cugier et al. (1994) where the effect of using OP opacities (Seaton et al. 1994) instead of OPAL opacities (Rogers & Iglesias 1992) is illustrated. This requires spectroscopic calibration of models obtained from time-series of two-colour photometric data.

In this paper, we address these questions by detailed analysis of [FORMULA]  Cet (HD 16582, HR 779, B2 IV). Both the nonadiabatic observables and mean stellar parameters are investigated using ground-based photometric data and UV spectro-photomeric observations collected by the International Ultraviolet Explorer (IUE) satellite.

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© European Southern Observatory (ESO) 1997

Online publication: October 15, 1997