Abstract
Nine helium rich sdO stars are found to show no trace of hydrogen on high resolution visual spectra. Effective temperatures derived from UV fluxes range from 42500 K to 80000 K. A dichotomy with respect to the C/N ratio is found which is reminiscent of the OBN and OBC stars near the main sequence. It is estimated that about 20% of the sdO stars are extremely helium rich. This fraction compares nicely with those of the (helium rich) DB white dwarfs (20%) and the helium rich central stars of planetary nebulae (less than 35%).
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© 1986 D. Reidel Publishing Company
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Heber, U., Drilling, J.S., Husfeld, D. (1986). UV- and Visual Spectroscopy of Nine Extremely Helium Rich Subluminous- O-Stars. In: Hunger, K., Schönberner, D., Rao, N.K. (eds) Hydrogen Deficient Stars and Related Objects. Astrophysics and Space Science Library, vol 128. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-4744-3_38
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DOI: https://doi.org/10.1007/978-94-009-4744-3_38
Publisher Name: Springer, Dordrecht
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