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Chandrasekhar mass explosions of white dwarfs as a model for type Ia supernovae and their contribution to cosmic nucleosynthesis
Although type Ia supernovae are widely applied as cosmological distance indicators and contribute significantly to the enrichment of the Universe with iron group elements, their physi- cal nature is not clear yet. The heterogeneous class of type Ia supernovae is divided into several subtypes according to their observational properties, and a whole variety of possible explosion scenarios has been put forward in order to explain these extraordinarily bright events. The focus of this work lies on the numerical modeling of explosions in Chandrasekhar mass carbon-oxygen white dwarfs as well as on the investigation of the nucleosynthesis yields of several explosion chan- nels. To this end, numerical simulations of the explosion, the propagation of radiation through the expanding debris, and the galactic chemical evolution of the Milky Way were conducted. It was found that, in line with earlier studies, deflagrations in Chandrasekhar mass white dwarfs are a viable model for type Iax supernovae, a subluminous subclass of type Ia supernovae. However, the parameter study employing different ignition conditions, central densities, metallicities, com- position and rigid rotation revealed that the very faint end of the subclass can not be reproduced. Furthermore, a set of gravitationally confined detonation simulations has been carried out. In this scenario an initial deflagration is followed by a detonation initiated near the surface of the white dwarf core. It could be shown that the synthetic observables do not agree with either normal or subluminous type Ia supernovae but that objects similar to SN 1991T might be explained by this explosion mechanism. Finally, the nucleosynthesis yields of various different explosion models were analyzed. This study shows that explosions in sub-Chandrasekhar mass white dwarfs with an accreted helium shell can contribute significantly to the abundance of manganese, zinc, and copper in the Universe and should be included in future galactic chemical evolution studies.
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500 Naturwissenschaften und Mathematik
500 Natural sciences and mathematics
520 Astronomie
520 Astronomy and allied sciences
530 Physik
530 Physics