Asymptotic Giant-Branch Evolution of a 0.6 m, Star

The evolution of a double shell source 0.6 M0 Population II star has been followed in detail through the asymptotic-branch phase into the region of the R-R diagram occupied by the nuclei of planetary nebula. No attempt has been made to suppress helium shell flashes. During the total of 14 relaxation oscillation cycles encountered, no convective mixing took place between the helium shell and the hydrogen-rich layers. A small amount of the products of hydrogen burning was mixed to the surface by an extensive convective zone that developed shortly after major flash peaks. Toward the end of the asymptotic-branch evolution the star spent a considerable time in the region of the H-R diagram occupied by RV Tauri-type stars in globular clusters. Subjects headings: interiors, stellar - population II stars - stellar evolution - variable stars