Gravity Modes in ZZ Ceti Stars. IV. Amplitude Saturation by Parametric Instability
نویسندگان
چکیده
منابع مشابه
Gravity-modes in Zz Ceti Stars Iv. Amplitude Saturation by Parametric Instability
ZZ Ceti stars exhibit small amplitude photometric pulsations in multiple gravity modes. As the stars cool their dominant modes shift to longer periods. We demonstrate that parametric instability limits overstable modes to amplitudes similar to those observed. In particular, it reproduces the trend that longer period modes have larger amplitudes. Parametric instability is a form of resonant 3-mo...
متن کاملGravity Modes in Zz Ceti Stars. Ii. Eigenvalues and Eigenfunctions
We report on numerical calculations of nonadiabatic eigenvalues and eigenfunctions for g-modes in ZZ Ceti variables. The spectrum of overstable l \ 1 modes delineates the instability strip. Its blue edge occurs where for the n \ 1 mode. Here u is radian frequency and is about 4 times the uq c B 1 q c thermal time at the bottom of the surface convection zone. As a ZZ Ceti cools, its convection z...
متن کاملGravity-modes in Zz Ceti Stars Iii. Eigenvalues and Eigenfuctions
We report on numerical calculations of nonadiabatic eigenvalues and eigenfunctions for g-modes in ZZ Ceti variables. The spectrum of overstable l = 1 modes delineates the instability strip. Its blue edge occurs where ωτc ≈ 1 for the n = 1 mode. Here ω is radian frequency and τc is about four times the thermal timescale at the bottom of the surface convection zone. As a ZZ Ceti cools, its convec...
متن کاملGravity-modes in Zz Ceti Stars Ii. Effects of Turbulent Dissipation
We investigate dynamical interactions between turbulent convection and g-mode pulsations in ZZ Ceti variables (DAVs). Since our understanding of turbulence is rudimentary, we are compelled to settle for order of magnitude results. A key feature of these interactions is that convective response times are much shorter than pulsation periods. Thus the dynamical interactions enforce near uniform ho...
متن کاملGravity-modes in Zz Ceti Stars I. Quasiadiabatic Analysis of Overstability
We analyze the stability of g-modes in variable white dwarfs with hydrogen envelopes. All the relevant physical processes take place in the outer layer of hydrogen rich material which consists of a radiative layer overlain by a convective envelope. The radiative layer contributes to mode damping because its opacity decreases upon compression and the amplitude of the Lagrangian pressure perturba...
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ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 2001
ISSN: 0004-637X,1538-4357
DOI: 10.1086/318234