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FUSE Observations of He-rich sdB StarsMost subdwarf B stars are extremely deficient in helium and selected light elements, but a minority are helium-rich. New evolutionary calculations suggest that these helium-rich sdB stars are the result of a delayed helium-core flash on the white dwarf cooling curve, which leads to extensive mixing between the hydrogen envelope and helium core. Such mixed stars should show greatly enhanced helium and carbon with respect to the other heavy elements. We have recently obtained FUSE spectra of two helium-rich sdB stars, PG1544+488 and JL87, revealing huge C Ill lines at 977 and 1176 A. Our analysis shows that PG1544+488 has a surface composition of 97% He, 2% C, and 1% N, in agreement with the new evolutionary scenario. While JL87 also reveals a large enrichment in carbon and nitrogen (1.4% and 0.4%, respectively), there is still a significant amount of hydrogen in its atmosphere.
Document ID
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Swiegart, A. V.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Lanz, T.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Brown, T. M.
(Space Telescope Science Inst. Baltimore, MD, United States)
Hubeny, I.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Landsman, W. B.
(Science Systems and Applications, Inc. Greenbelt, MD, United States)
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Subject Category
Meeting Information
Meeting: Extreme Horizontal Branch Stars and Related Objects
Location: Staffordshire
Country: United Kingdom
Start Date: June 16, 2003
End Date: June 20, 2003
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