Volume 484, Number 1, June II 2008
|Page(s)||29 - 42|
|Published online||01 April 2008|
Direct numerical simulations of the -mechanism
I. Radial modes in the purely radiative case
Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue Édouard Belin, 31400 Toulouse, France e-mail: email@example.com
Accepted: 17 February 2008
Context. We present a purely-radiative hydrodynamical model of the κ-mechanism that sustains radial oscillations in Cepheid variables.
Aims. We determine the physical conditions favourable for the κ-mechanism to occur inside a layer, with a configurable conductivity-hollow. We complete nonlinear direct numerical simulations (DNS) that initiate from these most favourable conditions.
Methods. We compare the results of a linear-stability analysis, applied to radial modes using a spectral solver, and a DNS, which is developed from a high-order finite difference code.
Results. We find that by changing the location and shape of the hollow, we can generate well-defined instability strips. For a given position in the layer, the amplitude and width of the hollow appear to be key parameters to vary to attain unstable modes driven by the κ-mechanism. The DNS, starting from the favourable conditions, confirm both the growth rates and the structures of linearly-unstable modes. Nonlinear saturation is produced by intricate couplings between excited fundamental mode and higher damped overtones.
Key words: hydrodynamics / instabilities / waves / stars: oscillations / methods: numerical
© ESO, 2008
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.