The Effect of Rapid Rotation on Main Sequence Line-Profile Variables

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Session 55 -- Pulsating Variables/Stellar Models
Display presentation, Thursday, 2, 1994, 9:20-6:30

[55.09] The Effect of Rapid Rotation on Main Sequence Line-Profile Variables

Maurice J. Clement (University of Toronto)

The line-profile variables observed on the upper main sequence are interpreted by some astronomers to be the manifestation of nonaxisymmetric oscillations. More specifically, many of these stars can be modelled by prograde (or corotating) equatorial waves. These are sectorial modes which in the absence of rotation have surface velocity distributions corresponding to simple spherical harmonics. Unfortunately, the velocity fields in the presence of rotation are much more difficult to predict. In this paper, I will report on the results of variational calculations which account for the effects of rapid rotation on the normal mode eigenfunctions of $15\,{\rm M}_{\odot}$ stellar models. The principal conclusion is that nonaxisymmetric modes couple only weakly to rotation and, consequently, they retain many of the geometrical properties that apply in the absence of rotation. In fact, it is not easy to detect the signature of rotation in the line-profile variations, especially for some long-period gravity modes of low radial order. This means that if the latter modes are the relevant ones then observers will not be making large errors in their mode identifications when they adopt the spherical harmonic model.

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