Nucleosynthesis and supernovae in massive stars

The evolution and explosion of stars heavier than 11 solar masses is explored. Particular emphasis is given to the factors affecting nucleosynthesis and the mass and nature of the collapsed remnant. The neutron star initial mass function will be bimodal with discontinuously larger characteristic masses expected for main sequence stars heavier than 19 M⊙ [the exact value depending upon the rate for 12C(α,γ)16O and whether carbon burns radiatively or convectively in the core]. Above some critical mass, black holes may be produced in otherwise successful supernovae. The ratio of heavy elements to helium ejected in such explosions depends critically upon the explosion energy. For this reason and others, observed values of dY/dZ cannot be used in a straightforward way to imply a limit on the mass of a star that explodes as a Type II supernova.