The Origin and Evolution of Helium-Rich White Dwarfs

James Liebert
1985 International Astronomical Union Colloquium  
AbstractWhite dwarfs with helium-rich atmospheres constitute about one fifth of the white dwarfs hotter than 12,000 K. They appear to have a mass distribution similar to the hydrogen atmosphere (DA) stars, and are similar in other properties. However, the temperature distribution exhibits a deficiency of DB/DO stars in the interval 25,000-45,000 K, which implies evolution in the dominant surface composition as the stars cool. The hottest group of transition DO white dwarfs are the pulsating
more » ... e the pulsating objects of the PG1159 class. The central star of Kl-16 is a related object, as may be the newly discovered very hot star H1504+65, which shows no detected surface features of either hydrogen or helium.
doi:10.1017/s0252921100090965 fatcat:hino6ickvfdvnlgtbff2bq4qmm