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 Teff = 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.
We have measured the Yb 3d 5/2 resonant hard x-ray photoemission spectra at the Yb L 3 edge of YbInCu 4 with the valence transition at T V = 42 K. The L 3 resonance effect in both Yb 2+ and Yb 3+ components in the Yb 3d 5/2 spectra is successfully observed at 70 and 20 K. We find that the feature of their constant initial state (CIS) spectra is described with the Fano profile. The feature of the CIS spectra is almost unchanged across T V .
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