Convective-core overshooting of massive stars

Larger convective core overshooting shifts the location of the compactness peak by 1-2M_{sun}_ to higher M_CO_. These core masses correspond to initial masses of 24M_{sun}_ (19M_{sun}_) and >~40M_{sun}_ (>~30M_{sun}_), respectively, in models with the lowest (highest) convective core overshooting parameter. In both high-compactness regimes, stars are found to collapse into black holes.

As the luminosity of the pre-supernova progenitor is determined by M_CO_, we predict blackhole formation for progenitors with luminosities 5.35<=log(L/L_{sun}_)<=5.50 and log(L/L_{sun}_)>=5.80. The luminosity range of black-hole formation from stars in the compactness peak agrees well with the observed luminosity of the red supergiant star N6946 BH1 that disappeared without a bright supernova and likely collapsed into a black hole.

While some of our models in the luminosity range log(L/L_{sun}_)=5.1-5.5 indeed collapse to form black holes, this does not fully explain the lack of observed SN IIP progenitors at these luminosities, i.e. the missing red-supergiant problem. The amount of convective boundary mixing also affects the wind mass loss of stars such that the lowest black hole mass are 15M_{sun}_ and 10M_{sun}_ in our models with the lowest and highest convective core overshooting parameter, respectively.

The compactness parameter, central specific entropy, and iron core mass describe a qualitatively similar landscape as a function of M_CO_, and we find that entropy is a particularly good predictor of the neutron-star masses in our models. We find no correlation between the explosion energy, kick velocity, and nickel mass production with the convective core overshooting value, but a tight relation with the compactness parameter.

We further show how convective core overshooting affects the pre-supernova locations of stars in the Hertzsprung-Russell diagram and the plateau luminosity and duration of SN IIP lightcurves.