SDSS White Dwarfs with Spectra Showing Atomic Oxygen and/or Carbon Lines
Abstract
We discuss 18 white dwarfs, one of which (G227-5) was previously known, whose SDSS spectra show lines of neutral and/or singly ionized carbon. At least two and perhaps four show lines of neutral or singly ionized oxygen. Apart from the extremely hot ``PG 1159'' stars, these are the first white dwarfs with photospheric oxygen detected in their optical spectra. The photometry strongly suggests that these stars lie in the 11,000-30,000 K temperature range of the helium-atmosphere DB white dwarfs, though only one of them shows weak neutral helium lines in the spectrum. Trigonometric parallaxes are known for G227-5 and another, previously known white dwarf (G35-26) showing atomic carbon lines, and they indicate that both are massive stars. Theoretical arguments suggest that all members of this class of rare white dwarfs are massive (~1 Msolar), and this finding could explain the paucity of massive DB white dwarfs.
- Publication:
-
The Astronomical Journal
- Pub Date:
- November 2003
- DOI:
- 10.1086/378911
- Bibcode:
- 2003AJ....126.2521L
- Keywords:
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- Stars: Abundances;
- Stars: Atmospheres;
- Stars: White Dwarfs