Astronomy & Astrophysics

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Issue		A&A Volume 435, Number 3, June I 2005
Page(s)		927 - 939
Section		Stellar structure and evolution
DOI		10.1051/0004-6361:20041817

A&A 435, 927-939 (2005)
DOI: 10.1051/0004-6361:20041817

Convection-pulsation coupling

II. Excitation and stabilization mechanisms in $\delta$ Sct and $\gamma$ Dor stars

M.-A. Dupret¹, A. Grigahcène¹, R. Garrido¹, M. Gabriel² and R. Scuflaire²

¹ Instituto de Astrofísica de Andalucía-CSIC, Apartado 3004, 18080 Granada, Spain
e-mail: ahmed@iaa.es
² Institut d'Astrophysique et de Géophysique de l'Université de Liè ge, Belgium

(Received 9 August 2004 / Accepted 23 January 2005)

Abstract
We apply here the Time Dependent Convection (TDC) treatment presented in our earlier paper in this series to the study of $\delta$ Sct and $\gamma$ Dor pulsating stars. Stabilization of the $\delta$ Sct p-modes at the red edge of the Instability Strip (IS) and the driving of the $\gamma$ Dor g-modes are explained by our models. Theoretical IS obtained with different values of the Mixing Length (ML) parameter $\alpha$ are compared to observations and a good agreement is obtained for $\alpha$ between 1.8 and 2. The influence of each term of our TDC treatment (perturbation of convective flux, turbulent pressure, and turbulent kinetic energy dissipation) on the eigenfrequencies and on the driving and damping mechanisms is investigated. Finally, we show that our TDC models predict the likely existence of hybrid stars with both $\delta$ Sct p-modes and $\gamma$ Dor g-modes oscillations.

Key words: stars: oscillations -- convection -- stars: interiors -- stars: variables: $\delta$ Sct -- stars: variables: general

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Convection-pulsation coupling

II. Excitation and stabilization mechanisms in Sct and Dor stars

II. Excitation and stabilization mechanisms in $\delta$ Sct and $\gamma$ Dor stars