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Browsing by Author "Jeffery, C. S"

Browsing by Author "Jeffery, C. S"

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  • Abundance analyses of cool extreme helium stars 
    Pandey, G; Kameswara Rao, N; Lambert, D. L; Jeffery, C. S; Asplund, M (Royal Astronomical Society, 2001-07)
    Extreme helium stars (EHes) with effective temperatures from 8000 to 13000K are among the coolest EHes and overlap the hotter R CrB stars in effective temperature. The cool EHes may represent an evolutionary link between ...
  • Abundance analysis of extreme helium stars 
    Pandey, G; Kameswara Rao, N; Lambert, D. L; Jeffery, C. S; Asplund, M (Astronomical Society of India, 2000)
    High resolution spectra were obtained for a sample of hydrogen-deficient stars which are hotter than the R CrB stars and cooler among the extreme helium stars (EHe). We believe that these stars are transition objects ...
  • Abundances of Neutron-Capture Elements in the Hot Extreme Helium Stars V1920 Cygni and HD 124448 
    Pandey, G; Lambert, D. L; Kameswara Rao, N; Jeffery, C. S (The American Astronomical Society, 2004-02-20)
    Analysis of Hubble Space Telescope Space Telescope Imaging Spectrograph ultraviolet spectra of two hot extreme helium (EHe) stars, V1920 Cyg and HD 124448, provides the first measurements of abundances of neutron-capture ...
  • On the Binary Helium Star DY Centauri: Chemical Composition and Evolutionary State 
    Pandey, G; Kameswara Rao, N; Jeffery, C. S; Lambert, D. L (IOP Publishing, 2014-10-01)
    DY Cen has shown a steady fading of its visual light by about one magnitude in the last 40 yr, suggesting a secular increase in its effective temperature. We have conducted non-local thermodynamic equilibrium (LTE) and LTE ...
  • SALT revisits DY Cen: a rapidly evolving strontium-rich single helium star 
    Jeffery, C. S; Kameswara Rao, N; Lambert, D. L (Oxford University Press on behalf of the Royal Astronomical Society, 2020-04)
    The hydrogen-deficient star DY Cen has been reported as an R CrB-type variable, an extreme helium star (with some hydrogen), and as a single-lined spectroscopic binary. It has been associated with a dramatic change in ...

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