Spectral analyses of DO white dwarfs and PG 1159 stars from the Sloan Digital Sky Survey

We present a model atmosphere analysis of ten new DO white dwarfs and five new PG 1159 stars discovered in the Sloan Digital Sky Survey DR1, DR2 and DR3. This is a significant increase in the number of known DOs and PG 1159 stars. DO white dwarfs are situated on the white dwarf cooling sequence from the upper hot end (Teff$\, \approx 120\,000$ K) down to the DB gap (Teff$\, \approx 45\,000$ K). PG 1159 stars on the other hand feature effective temperatures which exceed Teff$\,= 65\,000$ K with an upper limit of Teff$\,= 200\,000$ K and are the proposed precursors of DO white dwarfs. Improved statistics are necessary to investigate the evolutionary link between these two types of stars. From optical SDSS spectra effective temperatures, surface gravities and element abundances are determined by means of non-LTE model atmospheres.