Evolution and Final Fate of Solar Metallicity Stars in the Mass Range 7–15 M ⊙. I. The Transition from Asymptotic Giant Branch to Super-AGB Stars, Electron Capture, and Core-collapse Supernova Progenitors

Abstract

According to a standard initial mass function, stars in the range 7–12 M ⊙ constitute ∼50% (by number) of the stars more massive than ∼7 M ⊙, but in spite of this, their evolutionary properties, and in particular their final fate, are still scarcely studied. In this paper, we present a detailed study of the evolutionary properties of solar metallicity nonrotating stars in the range 7–15 M ⊙, from the pre-main-sequence phase up to the presupernova stage or an advanced stage of the thermally pulsing phase, depending on the initial mass. We find that (1) the 7.00 M ⊙ star develops a degenerate CO core and evolves as a classical asymptotic giant branch (AGB) star in the sense that it does not ignite the C-burning reactions, (2) stars with initial mass M ≥ 9.22 M ⊙ end their lives as core-collapse supernovae, (3) stars in the range 7.50 ≤ M/M ⊙ ≤ 9.20 develop a degenerate ONeMg core and evolve through the thermally pulsing super-AGB phase, (4) stars in the mass range 7.50 ≤ M/M ⊙ ≤ 8.00 end their lives as hybrid CO/ONeMg or ONeMg WDs, and (5) stars with initial mass in the range 8.50 ≤ M/M ⊙ ≤ 9.20 may potentially explode as electron-capture supernovae.