Supernova models

By comparing the observed chemical abundance ratios to supernova model yields, one can calculate , the ratio of the number of SNe la to SNe II events that fit the observations and the synthesized mass of the elements from the model yields. In a study adopting the same analysis techniques as those performed here, [5] found large values of for a trio of low-a stars of [Fe/H] -2. Employing the abundances derived in this study of stars with comparable metallicities, I find that the metal-poor systems presented here possess a- and iron-peak abundances (and based on Na, Mg, Si and Fe) consistent with those observed in metal-poor stars of the MWG (e.g., [6]). 

A pre-supernova model of a 9Mq star is taken from Nomoto [3], which forms a 1.38 Mq O-Ne-Mg core. We link this core to a one-dimensional implicit La-grangian hydrodynamic code with Newtonian gravity. The equation of state of nuclear matter (EOS) is taken from Shen et al. [4]. We find that a very weak explosion results, where no r-processing is expected. In order to examine the possible operation of the r-process in the explosion of this model, we artificially obtain an explosion with a typical energy of 1051 ergs by application of a multiplicative factor (= 1.6) to the shock-heating term in the energy equation. 

The supernova models utilized below have all been generated by S. Woosley using the Kepler [7] supernova code. The evolution is followed with Kepler until the expansion becomes essentially homologous. At this point the Kepler information is transferred to the spectrum code. It is important to emphasize that once the supernova model has been selected the predicted spectra are generated without adjustable parameters. The adjustable parameters of the model are on the whole those with direct astrophysical relevance, for example the initial stellar mass and amount of mass loss. It is,.of course, feasible and useful to use the comparison of the observed and predicted spectra to refine the supernova model. This, however, has not yet been done except in a rough way. At present, the nebular spectra have been used only to choose broad classes of feasible models and mle out others. For example, the He detonation models for SNIa have been ruled out on the basis of the spectrum[8]. The results presented, therefore, must be viewed accordingly as generic to a whole class of models whose details are still unresolved. 

H.-Th. Janka, R. Buras, F.S. Kitaura Joyanes, et al. Core-Collapse Supernovae Modeling between Pragmatism and Perfectionism. In Proc. 12th Workshop on Nuclear Astrophysics. 

With temperature, density and Ye as free parameters, many choices of initial NSE compositions may clearly be made, involving a dominance of light or heavy nuclides, as illustrated in Fig. 24. However, in view of its relevance to the supernova models, an initial NSE at temperatures of the order of 1010 K is generally considered. It favours the recombination of essentially all the available protons into a-particles (the region noted NSE n,o in Fig. 24). The evolution of this initial composition to the stage of charged-particle induced reaction freeze-out has been analyzed in detail by [60], and we just summarize here some of its most important features that are of relevance to a possible subsequent r-process ... 

The supernova explosions are still poorly understood, and it is still a long way to go to their successful simulations based on less uncertain pre-supernova models. Here again, the multi-dimensional treatment of a variety of physical effects, including rotation, magnetic fields, instabilities of different origins, and the transport of neutrinos, appears to be required. 

The calculation of p-process yields from a variety of Chandrasekhar mass Type I supernova models of the deflagration or delayed detonation types, as well as of sub-Chandrasekhar He-detonation models. In the latter case, a... 

Supernova events as well as pre-supernova stages of stars play important roles in cosmochemistry. However, a number of aspects of astrophysics of both pre-supernova and supernova stages of evolution of massive stars remain unclear, as emphasized by Marcel Arnould (this volume). A major challenge comes from the uncertainties in the rates of some nuclear reactions and of weak interaction processes. Multi-dimensional simulations, especially of the late presupernova phases, are expected to be particularly helpful to understand these processes. Similarly, considerable efforts are still required for successful simulations of supernova explosions based on less uncertain pre-supernova models. Here again, the multi-dimensional treatment of a variety of physical effects, including rotation, magnetic fields, instabilities of different origins, and the transport of neutrinos needs careful inclusion. 

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