Analysis of the hydrogen deficient helium star HD 168476

Abstract

Employing high dispersion spectrographic material, a chemical and physical analysis of the atmosphere of the extreme helium star HD 168476 is made. Log gf values from the National Bureau of Standards compilation were preferentially used. For the singly ionized elements of the iron group, Warner's values corrected as suggested by Milone-Milone were used. It was almost impossible to derive neither an excitation temperature nor a ionization one, as quite different values result depending on the element. The value T=12300 K was finally adopted. The turbulent velocity (its most probably value) is also poorly determined: 0 ≤ Vₜ ≤ 20 km/sec; the mean weighted value (as derived from several elements) is Vₜ=5 km/sec. The uncertainty in Vₜ affects abundances as much as 0.6 dex. The abundances we have found are in good agreement with the values reported in Hill's classical paper. This paper will be published in full elsewhere.