title: A white dwarf with an oxygen atmosphere.
abstract: Stars born with masses below around 10 solar masses end their lives as white dwarf stars. Their atmospheres are dominated by the lightest elements because gravitational diffusion brings the lightest element to the surface. We report the discovery of a white dwarf with an atmosphere completely dominated by oxygen, SDSS J124043.01+671034.68. After oxygen, the next most abundant elements in its atmosphere are neon and magnesium, but these are lower by a factor of ≥25 by number. The fact that no hydrogen or helium are observed is surprising. Oxygen, neon, and magnesium are the products of carbon burning, which occurs in stars at the high-mass end of pre-white dwarf formation. This star, a possible oxygen-neon white dwarf, will provide a rare observational test of the evolutionary paths toward white dwarfs.
authors.affiliation: Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-900 Porto Alegre, RS, Brazil. kepler@if.ufrgs.br.
authors.forename: S O
authors.initials: SO
authors.lastname: Kepler
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany.
authors.forename: Detlev
authors.initials: D
authors.lastname: Koester
authors.affiliation: Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-900 Porto Alegre, RS, Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Ourique