Progenitor Structures

Results of several model calculations let argue, that at the collapse phase there might exist two distinct families of core structures: (1) progenitor stars with a small and compact core (iron or O-Ne-Mg) at low entropy ($S < 1$ Boltzmann constant per baryon), which show a steep density profile at the outer mantle. (2) progenitor stars with a more massive core at high entropy ($S \geq 1$), which show a slower decay of the density profile [#!abjhbf!#]. Fig. shows the density profile as a function of the interior mass coordinate. The first core-family (11, 12, 15$M_{\odot}$) and the second one (20, 25$M_{\odot}$) are clearly distinguishable. The main differences between the two core structures are, that the smaller cores accumulate mass from outer layers more slowly, but explode easier. For heavier cores, the mass accretion rate $\dot{M}$, i.e. the capability to accumulate mass from the outer layers of the star can be large enough to slow down the explosion and even abort the supernova [#!abjhbf!#].

Figure: Density profile as a function of interior mass up to $2 M_{\odot}$ for different models performed by (Weaver and Woosley, 1994). Note the different behavior of the density profile for the two families of core structures. See text for details. Picture from [#!abjhbf!#]