1994A&A...286..463D

The discovery of a new PG 1159 star by follow-up spectroscopy of candidates selected from objective-prism plates of the Hamburg Schmidt Survey is presented. From a NLTE model atmosphere analysis an effective temperature of 65 000 K and a surface gravity of logg=7.0 is determined, which together with the extreme helium abundance (H/He<1 by number) place HS 0704+6153 in the region of hot DO white dwarfs. The high carbon and oxygen abundances (C/He=0.2, O/He∼0.05 by number), however, are typical for PG 1159 stars. Its effective temperature is by far lower than that of any other PG 1159 star. HS 0704+6153 therefore is in the transition stage between the PG 1159 stars and the DO white dwarfs, it hence is an ideal object to study the gravitational settling of metals in helium-rich atmospheres.