Multiwavelength studies of β Cephei stars: δ Ceti.

Abstract

We discuss diagnostic aspects that follow from identification of the driving mechanism for the pulsation of β Cephei stars by an analysis of the well-observed star δ 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 Z=0.02 fit the observations best. We find that δ Ceti is a star pulsating in the first overtone (p_2_) of the radial (l=0) mode. The luminosity of this star is in the range of 4.04<=logL/L_sun_<=4.16 and mass M=10.3+/-0.4M_sun_. We also discuss how these parameters can be improved using nonadiabatic observables.