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NLTE-Analysis of Three Extremely Helium-Rich O-Type Subdwarfs

Published online by Cambridge University Press:  12 April 2016

C. Husfeld ,
U. Heber  and
J.S. Drilling
C. Husfeld
Affiliation:
Universitätssternwarte, München, F.R.G.
U. Heber
Affiliation:
Inst. f. theor. Physik u. Sternwarte, Kiel, F.R.G.
J.S. Drilling
Affiliation:
Louisiana State University, Baton Rouge, U.S.A.

Abstract

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Three extremely helium-rich sdO stars (LSE 153, LSE 259 and LSE 263) were analyzed spectroscopically by means of detailed NLTE model atmospheres. These stars are very hot, with effective temperatures ranging from 70000 to 75000 K and gravities between log g = 4.4 and 4.9. Upper limits for the hydrogen abundance were also derived. The evolutionary status of the sdO stars is discussed and it is concluded that they evolve from the asymptotic giant branch towards the white dwarf stage. A possible evolutionary link between these hot stars and the extreme helium stars of spectral type B is discussed.

Type
VII Related Objects
Information
International Astronomical Union Colloquium , Volume 87: Hydrogen Deficient Stars and Related Objects , 1985 , pp. 353 - 357
Copyright
Copyright © Reidel 1986

References

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