New approach to the study of quasi-normal modes of rotating stars

We propose a new method to study the quasinormal modes of rotating relativistic stars. Oscillations are treated as perturbations in the frequency domain of the stationary, axisymmetric background describing a rotating star. The perturbed quantities are expanded in circular harmonics, and the resulting 2D equations they satisfy are integrated using spectral methods in the (r,θ) plane. The asymptotic conditions at infinity, needed to find the mode frequencies, are implemented by generalizing the standing wave boundary condition commonly used in the nonrotating case. As a test, the method is applied to find the quasinormal mode frequencies of a slowly rotating star.