Normal modes of oscillation for rotating stars. IV - Nonaxisymmetric variational solutions for 15 solar mass models

A variational principle is generalized to incorporate nonaxisymmetric modes of oscillation and applied to a sequence of rigidly rotating 15-solar-mass stellar models. Toroidal-type basis vectors are introduced and used in conjunction with irrotational and quasi-poloidal basis functions to model the nonaxisymmetric pressure, Kelvin, and gravity modes. Numerical results are presented based on 75 typically variational coefficients, and the eigenfrequencies and the eigenfunctions are examined for the effects of the t-type basis vectors. It is found that, with the exception of very fast rotation, the pressure- and gravity-mode periods can be computed quite accurately without the toroidal vectors, even though the internal motions can assume considerable toroidal characteristics with increasing rotation. It is also found that, under the influence of rotation, the sectorial modes couple only weakly to spherical harmonics of adjacent order. 21 refs.