Mode Identification in beta Cephei Stars from Visual and UV Observations I. beta Cephei, delta Ceti and sigma Scorpii
Abstract
Visual and UV light amplitudes, radial velocities and phase shifts are discussed for pulsating stars using a method elaborated by Watson (1988). Model calculations are based on the standard atmosphere models taking into account temperature and pressure changes during pulsation cycle. Consistent set of parameters are presented for three beta Cephei variables. The best fit solutions yield fundamental radial mode (l=0, Q=0^d037) for single periodic stars (beta Cephei and delta Ceti) and for P_2 component of sigma Scorpii. For P_1 component of sigma Sco we obtain quadrupole mode, l=2. The first overtone with almost equally good fit predicts about 20percent larger stellar radii and lower effective temperatures. Pulsations are nonadiabatic with the ratio of fractional temperature amplitude to fractional radius amplitude, B equal to 1.93 (beta Cep), 3.02 (delta Cet), 1.75 (sigma Sco, P_2), whereas adiabatic value is B_{ad}=4.42. All these numbers correspond to the fundamental radial modes. Larger Bvalues are found for the first overtones. For P_1 component of sigma Sco we obtain B=1.27. The observed phase shifts between light curves at different wavelength bands and radial velocity curves result in the phase shift between temperature and radius variations, psi_T equal to (in radians) 3.05 (beta Cep), 3.315 (delta Cet), 3.111 (sigma Sco, P_2 ) and 3.00 (sigma Sco, P_1).
 Publication:

Acta Astronomica
 Pub Date:
 July 1992
 Bibcode:
 1992AcA....42..191C
 Keywords:

 B Stars;
 Cepheid Variables;
 Radial Velocity;
 Stellar Oscillations;
 Ultraviolet Astronomy;
 Visual Observation;
 Stellar Atmospheres;
 Stellar Models;
 Stellar Temperature;
 Astrophysics