Non-radial oscillations in rotating intermediate mass stars

Abstract

In this work I investigate the influence of rotation on pulsation frequencies in upper main sequence stars. I use 2D stellar structure models and a 2D linear adiabatic pulsation code to calculate pulsation frequencies for both uniformly and differentially rotating 10 [Special characters omitted.] ZAMS models. Current techniques for these calculations often assume that the pulsation mode can be modelled using a single spherical harmonic and that the rotation rate is slow enough for second order perturbation theory approaches to be valid. These techniques require the rotation rate to be small enough to be considered a small linear perturbation. Using my 2D models, I am able to determine independent limits on the rotation rates for which these techniques are valid. These limits depend strongly on the mode and property in question, and range from 50-400 km sˉ¹. In general, uniform rotation decreases both the frequencies and the large separations, but produces increases in the small separations. In differentially rotating models, the frequencies may either increase or decrease, depending on the mode. Since these variations move in opposite directions, it may be possible to constrain the interior angular momentum distribution from stellar pulsations. Unfortunately, the differences are small, and the observational challenges may be insurmountable. Finally, I investigate how the distortion in the shape of the eigenfunction influences photometric mode identification techniques. Increasing rotation increases the variation in photometric mode identification as a function of inclination, with the result that it may be impossible to rule out certain modes.