Abundance patterns in hot subdwarf B stars: The case of carbon

P. Chayer, G. Fontaine, F. Wesemael, J. Dupuis, J. W. Kruk, E. M. Green

Research output: Chapter in Book/Report/Conference proceedingConference contribution


One of the most puzzling phenomena observed at the surface of sdB stars is their abundance nomalies. For instance, high-resolution optical spectroscopy shows that the C abundance is ower than the solar abundance by about a factor of ten on average. A few stars, however, show a olar abundance or an abundance higher than solar. Although optical spectroscopy allows the measurement f relatively high C abundance, it fails to provide stringent upper limits when no C linesare detected. The Far Ultraviolet Spectroscopic Explorer (FUSE) comes to the rescue when no Clines are detected in the optical, because it is 1,000 times more sensitive than the VLT for the purposeof measuring very small amounts of C in the atmospheres of sdB stars. We measure the Cabundance in the FUSE spectra of 30 stars. We confirm the C abundance trend reported in previousstudies, but report the disappearance of C in five stars. The upper limits that we measure for thesestars are about four orders of magnitude lower than the solar abundance. The observation of verylow C abundance suggests that the normal equilibrium between gravitation and radiative levitation has been disrupted, perhaps by a weak stellar wind.

Original languageEnglish (US)
Title of host publicationFuture Directions in Ultraviolet Spectroscopy - A Conference Inspired by the Accomplishments of the Far Ultraviolet Spectroscopic Explorer Mission
Number of pages3
StatePublished - 2009
EventFuture Directions in Ultraviolet Spectroscopy Conference - Annapolis, MD, United States
Duration: Oct 20 2008Oct 22 2008

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


ConferenceFuture Directions in Ultraviolet Spectroscopy Conference
Country/TerritoryUnited States
CityAnnapolis, MD


  • Diffusion
  • Stars: Abundances
  • Techniques: Spectroscopic

ASJC Scopus subject areas

  • General Physics and Astronomy


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