Abstract

Contributed Talk - Splinter CloseBinaries   (MW-0250)

A treasury of hot white dwarfs

Semih Filiz, Nicole Reindl, Klaus Werner
University of Heidelberg, University of Tübingen

Hydrogen-rich white dwarfs (WDs) dominate the WD population, yet their youngest and hottest members (Teff ≥ 50 kK) are intrinsically rare due to their short evolutionary timescales. As a result, our understanding of the physical processes governing these early cooling stages remains limited by low-number statistics. Within the HST large program 17112, we obtained 85 far-UV spectra of hot, H-rich WDs. This unique dataset enables robust determinations of effective temperatures and metal abundances from fully metal line-blanketed, non-local thermodynamic equilibrium model atmospheres. The sample includes 7 close and 5 wide binary systems, as well as 9 central stars of planetary nebulae and 3 objects exhibiting the ultra-high excitation (UHE) phenomenon. We present first results on how metal abundance patterns evolve along the early WD cooling sequence, providing new observational constraints on diffusion theory. We further explore the impact of close binary evolution on atmospheric composition.