Stability of g-modes in rotating B-type stars - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado

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Abstract: We have studied the stability of low degree $g$-modes in uniformly rotatingB-type stars, taking into account the effects of the Coriolis force and therotational deformation. From an analysis treating rotation frequency as a smallparameter it is found that slow rotation tends to $destabilize$ highradial-order $retrograde$ $g$-modes, although the effect is very small orabsent for relatively low order modes. Calculating eigenfrequencies at selectedrotation rates, we find, on the other hand, that rapid rotation tends to$stabilize$ $retrograde$ $g$-modes. The stabilizing effect appears stronger forless massive B-type stars having low effective temperatures. If we changerotation rate continuously, the frequency of a $g$-mode belonging to $l-, m$crosses frequencies of other $g$-modes belonging to $l-, m$. If the parity ofthe two encountering modes are the same, they interact each other and thestability i.e., imaginary part of eigenfrequency of each mode is modified.Using an asymptotic method we discuss the property of such mode crossings andcouplings. For rapidly rotating stars mode couplings are important for thestability of low degree $g$-modes. In particular, we find that thestabilization of retrograde $g$-modes in rapidly rotating stars is due to manystrong mode couplings, while %prograde sectoral% modes are exceptionally immuneto the damping effects from the mode couplings.

Autor: Aprilia, Umin Lee, Hideyuki Saio


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