The spectra of helium stars, II. An abundance analysis of three helium stars
Abstract
Abundances in the atmospheres of the helium stars HD 168476, HD xz 8 and BD + are determined relative to helium with the aid of the Milne-Eddington curve of growth, and on the assumption that the opacity is entirely due to helium and electrons. Relative to the total masses of their atmospheres, the helium abundance has the value expected for complete hydrogen exhaustion. Upper limits for the hydrogen and oxygen abundances show that hydrogen is present only in negligible quantities, while oxygen has at the most 1/4 to 1/3 the normal abundance. Carbon, and possibly neon and nitrogen, are overabundant, while other light elements have similar abundances to those in normal stars. Elements of the iron peak in HD 168476 appear to be about 10 times overabundant, but it is suspected that their lines may be formed in a cool, outer shell.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- 1965
- DOI:
- 10.1093/mnras/129.2.137
- Bibcode:
- 1965MNRAS.129..137H