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Effects of moderate rotation on stellar pulsation
I. Third order perturbation formalism
F. Soufi 1,
* 1 and
Received 20 October 1997 / Accepted 9 March 1998
Interpretation of the available ground-based and forthcoming space observations of multiperiodic variable stars require accurate computations of oscillation frequencies. Typical rotational equatorial velocities of upper main sequence stars range between 50 and 200 km/s and the effect of rotation on the oscillation frequencies of these stars must be included. The rotation can still be considered as a perturbation, provided the expansion used in the perturbation method is carried out far enough to provide frequencies accurate enough to match that of the observations. For that purpose, we develop here a perturbation formalism for adiabatic oscillations of moderately rotating stars which is consistently valid up to third order in the rotation rate.
The formalism includes the case of near-degeneracy i.e. when the frequencies of two (or three) oscillation modes happen to be close to each other. This occurs systematically for and p -modes. Near-degeneracy leads to spherical harmonic mixing and affects frequencies. Consequences for mode identification are discussed.
Key words: stars: oscillations stars: rotation ffi Scu stars: variables: other
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© European Southern Observatory (ESO) 1998
Online publication: June 2, 1998