Abundances in Two Horizontal-Branch a Stars
Abstract
Two horizontal-branch A stars, HD 86986 and HD 109995, have been analyzed spectroscopically by a combination of coarse- and fine-analysis techniques with spectrophotometric scans. The physical parame- ters, in Tables 1 and 6, include space motions near 350 km sec~, effective temperatures near 78000 K, and low surface gravity, log g = 3.0. The rotational velocities are small. The stars were compared differentially with HD 161817, which was analyzed by Kodaira who used a model atmosphere. The metal deficiencies, with respect to the Sun, for all three stars are given in Table 9. The mean values for thirteen elements were log~o (*)/~(o) = -1.54 (HD 86986), -1.76 (HD 109995), and -1.16 (HD 161817). The different nucleosynthetic processes show a systematic trend, similar to that found in the very metal-poor giant HD 122563. The a-nuclei (Mg, Ca, Si) are least deficient, the s-process (Sr, Y, Zr, Ba) most deficient, and the differences are largest in the most metal-poor star. An analysis of carbon and oxygen, using lines near the limit of detectability, shows them in high abundance, relative to the metals
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 1969
- DOI:
- 10.1086/149889
- Bibcode:
- 1969ApJ...155..525K