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Intermediate Helium Stars: Atmospheric Parameters, Oblique Rotators and Shells

Published online by Cambridge University Press:  12 April 2016

K. Hunger
K. Hunger*
Affiliation:
Institut für Theoretische PhysikundSternwarte der UniversitatKiel Olshausenstr. 40, 2300 Kiel, F.R.G.

Extract

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Intermediate helium stars are defined by

nHe/nH being the number ratio of He over H. The upper bound which separates the intermediates from the extremes is well-defined (see Sect. 7), whereas the lower bound is rather soft.

The first intermediate helium star discovered was Sigma Ori E (Greenstein and Wallerstein, 1956). Since then, 23 intermediates with V ≤ 1lm have been found (see the list of Walborn, 1983 and also the Annex), mostly through surveys such as that by McConnell et al. (1970) and McConnell (1972). (To this list, the newly discovered object SB 939, Langhans and Heber, 1985, should be added.) It is anticipated that a substantial fraction has as yet escaped detection. The spectral type centres around B2V while nHe/nH is typically of the order of unity.

Type
VI Intermediate Helium Stars
Information
International Astronomical Union Colloquium , Volume 87: Hydrogen Deficient Stars and Related Objects , 1985 , pp. 260 - 276
Copyright
Copyright © Reidel 1986

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