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The helium-rich stars of early spectral type
Astrophysics and Space Science, 1970The properties of the known helium-rich stars of early type are reviewed and the elemental abundances are analyzed. Current evolutionary theories of mixing and mass loss may explain the origin of these stars.
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Periodic spectrum variations in helium-rich stars
Publications of the Astronomical Society of the Pacific, 1982Spectroscopic observations of four helium-rich stars are presented. In HD 37776, antiphase variations of Si III and He I have been found, which represent another point of similarity to the Ap phenomenon. The remarkable H-alpha emission variations in Sigma Ori E are illustrated with uniform phase coverage, and strict periodicity over a five-year ...
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A Survey of Spectral Morphology and Rotational Velocities Among the Helium-Rich Stars.
Astrophysical Journal, 1983 A spectroscopically homogeneous listing of all known members of the helium-rich B star category is presented together with uniform estimates of their rotational velocities. Equivalent widths of hydrogen, helium, and metal lines in the spectra of the helium-rich and comparison stars are given.
N R Walborn
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Continuum Observations of Some Hot Helium-Rich Stars
Publications of the Astronomical Society of the Pacific, 1973Measurements are presented of the continuous energy distributions of six hot, helium-rich stars. The data have been used to determine the size of the Balmer discontinuities in all pro. gram stars and a search has been made for evidence for the presence of the helium discontinuity at A3422.
Jeffrey D. Rosendhal, Edward G. Schmidt
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The possible effect of diffusion in helium-rich subdwarf O stars
AIP Conference Proceedings, 2010The effect of a thin surface convection zone due to the partial ionization of helium on the results of diffusion calculations for helium‐rich subdwarf O stars is discussed for the stellar parameters Teff = 40000 K, logg = 6.0 and M*0.5 M⊙. An initial composition according to a late hot‐flasher scenario has been assumed.
Klaus Unglaub, Klaus Werner, T. Rauch
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The Evolution of Super-Helium-Rich 2 M_{sun} Stars
Publications of the Astronomical Society of the Pacific, 1971Evolutionary calculations are presented for three 29M0 configurations, two having super- helium -rich compositions, (X, Y, Z) = (0.30, 0.69, 0.01) and (0.30, 0.695, 0.005), and one a moderately helium-rich composition (0.60, 0.39, 0.01). The Z = 0.005 configuration is evolved past core helium exhaustion, the others only past core helium ignition ...
James W. Liebert +3 more
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UV- And Visual Spectroscopy of Nine Extremely Helium Rich Subluminous-O-Stars
International Astronomical Union Colloquium, 1985AbstractNine 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
U. Heber, J. S. Drilling, D. Husfeld
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Are Helium-Rich Subdwarf B Stars The Products of White Dwarf Mergers?
2003The He-rich sdB stars were originally identified as sdO(D) stars in the Palomar-Green survey of faint blue stars [4]. They have also been classified as He-sdB [8] and sdB4 [3]. A partial list of stars in this class was given by [6]. Spectroscopically He-sdB stars have very weak or no Balmer lines and strong He I absorption lines.
A. Ahmad, C. S. Jeffery, V. M. Woolf
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The helium-rich star HD 184927
Publications of the Astronomical Society of the Pacific, 1973N. A. Higginbotham, P. Lee
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