THE NUCLEOSYNTHETIC IMPRINT OF 15–40M☉PRIMORDIAL SUPERNOVAE ON METAL-POOR STARS

Abstract

The inclusion of rotationally induced mixing in stellar evolution can alter the structure and composition of pre-supernova stars. We survey the effects of progenitor rotation on nucleosynthetic yields in Population III and II supernovae (SNe) using the new adaptive mesh refinement code CASTRO. We examine piston-driven spherical explosions in 15, 25, and 40 M☉ stars at Z = 0 and 10−4 Z☉ with three explosion energies and two rotation rates. Rotation in the Z = 0 models resulted in primary nitrogen production and a stronger hydrogen burning shell which led all models to die as red supergiants (in contrast to the blue supergiant progenitors made without rotation). On the other hand, the Z = 10−4 Z☉ models that included rotation ended their lives as compact blue stars. Because of their extended structure, the hydrodynamics favors more mixing and less fallback in the metal-free stars than the Z = 10−4 models. As expected, higher energy explosions produce more enrichment and less fallback than do lower energy explosions, and at constant explosion energy, less massive stars produce more enrichment and leave behind smaller remnants than do more massive stars. We compare our nucleosynthetic yields to the chemical abundances in the three most iron-poor stars yet found and reproduce the abundance pattern of one, HE 0557−4840, with a zero metallicity, 15 M☉, 2.4 × 1051 erg SN. A Salpeter IMF-averaged integration of our yields for Z = 0 models with explosion energies of 2.4 × 1051 erg or less is in good agreement with the abundances observed in larger samples of extremely metal-poor (EMP) stars, provided 15 M☉ stars are included. Since the abundance patterns of EMP stars likely arise from a representative sample of progenitors, our yields suggest that 15–40 M☉ core-collapse SNe with moderate explosion energies contributed the bulk of the metals to the early universe.