Gravity Modes in ZZ Ceti Stars. IV. Amplitude Saturation by Parametric Instability
Gravity Modes in ZZ Ceti Stars. IV. Amplitude Saturation by Parametric Instability
ZZ Ceti stars (also known as DAV 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 …