Contributed Talk - Splinter HotStars

The giant-dwarf connection

D. Hoyer
Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, 72076 Tübingen, Germany

The Asymptotic Giant Branch (AGB) phase is one of the most complex and yet not fully understood phase in stellar evolution. Spectral analyses of hydrogen-deficient AGB descendants yield constraints on nuclear processes in that phase - a pre-requisite to understand AGB stellar evolution. The DO-type white dwarf RE 0503-289 was discovered in the ROSAT all-sky EUV survey two decades ago. Analyses of extreme and far-ultraviolet spectra of RE 0503-289 allowed to identify many metal lines up to the trans-iron elements. Thus, RE 0503-289 may be a rosetta stone to understand AGB nucleosynthesis and the post-AGB stellar evolution. To investigate its uniqueness, we selected three stars close to RE 0503-289 in the log T_\texteff - \log g plane. These are the PG 1159-type star PG 1707+427 and the two DO-type white dwarfs PG 0109+111 and WD 0111+002. We present a NLTE spectral analysis and discuss their evolution.