Pulsations of pre-white dwarfs with hydrogen-dominated atmospheres

We carried out a fully non-adiabatic analysis for nonradial oscillations of pre-white dwarfs evolved from the post-Asymptotic Giant Branch (AGB) with hydrogen-dominated envelopes. It is shown that nuclear reactions in the hydrogen burning shell excite low-degree g-modes in the period range of about 40–200 s for the pre-white dwarf models with T eff = 40000 K–300000 K. It is also shown that the amount of hydrogen has a significant influence on the instability domain of such pre-white dwarfs in the Hertzsprung-Russel (H-R) diagram. Thus, the thickness of hydrogen-dominated envelopes may be well constrained by observing the presence of the g-mode oscillations.