Nucleosynthesis Problems from the Subdwarfs γ Pav and ζ1Ret.
I. J. Danziger · The Astronomical Journal · 1965
The spectra of the southern subdwarfs 7 Pav and ~1Ret have been investigated at high dispersion. A curve of growth analysis relative to the integrated sun gave results of some interest in the theory of element production. 7 Pav showed an underabundance of the elements lighter than nickel by a factor of 0.7 in the logarithm and ~1Ret for the same elements a factor of 0.4. In both stars the carbon under abundance obtained from the rotational lines of the CH molecule was considerably more than for the other elements-1 .3 in the logarithm for 7 Pav and 0.8 for ~1Ret. Here the problem is that a-process elements such as Mg and Ca do not show the same effect. Another result of interest is that Mn is not more underabundant than Fe a result which was obtained for other metal-deficient dwarfs by WaIler- stein (Astrophys. J. Suppl. 6, 407, 1963). The heavy rare earth elements in both stars are more under- abundant than the iron group elements. The availability of accurate slow-neutron capture cross sections cr has allowed the construction of Na versus the atomic weight A diagrams. Recent theory of the S process by Seeger et al. (Astrophys. J. Suppl. 11, No. 97.) allows an observational test to be made. The data for 7 Pav as well as data for the sun, HD 116713, HD 83548, HD 26, and HD 201626 shows a series of obj ects containing material with difterent histories of slow-neutron flux exposures. The consequent changes in the shapes of the Na vs A diagrams strongly suports the present theory of slow neutron capture producing the s-process elements.