Surface motions of the Beta Cephei stars

A number of techniques for the identification of the pulsation modes operative in variable stars are explored theoretically and applied to some members of the #betta# Cephei group. The techniques are: use of the relative amplitudes and phases of the light, colour and radial velocity variatons; monitoring for variations in linear polarization; and comparison of observed line profiles with those synthesized theoretically for particular nonradial modes. A corrected Baade-Wesselink formula is obtained and the mode identification capabilities of the resulting Baade-Wesselink coefficients are investigated. From the application of the mode identification method it is inferred that the singly-periodic stars are radial pulsators. A hydrodynamic envelope pulsation model constructed indicates that nonlinear wave propagation of underlying sinusoidal motions into the outer envelope of a large amplitude radial pulsator may generate strong atmospheric shock waves