Numerical Sensitivity of Nonlinear Stellar Pulsation Computations
The limit cycle properties of pulsating stellar models are studied in the context of spatial zoning and artificial viscosity. Two standard models representing the RR Lyrae and 8 Cephei stars are thoroughly tested. At moderate amplitudes the strong shocks are shown to be confined to the hydrogen ionization zone, but most of the ‘shock’ dissipation originates from the nonviolent layers beneath this zone, where shocks should not exist. The limit cycle behavior (amplitude, velocity and light curves, stability) depends on the artificial viscosity and on the zone number and distribution. Comparison of our Lagrangean code with other non-Lagrangean codes for the same models leads to the conclusion that they all give very similar results if the mass shells are distributed properly in the Lagrangean code. It is very important to implement a more accurate numerical treatment of shocks in order to clarify the cause of the amplitude limitation.
KeywordsVelocity Curve Mass Shell Stellar Model Artificial Viscosity Spatial Zoning
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