The formation of type Ia supernovae: theory vs. observation

Type Ia supernovae (SNeIa), the most powerful events in the universe, are critical for cosmology and the chemical evolution of galaxies. They are caused by the thermonuclear explosion of white dwarfs in binary stars, which are no longer able to support themselves due to exceeding a critical mass. The formation mechanism of SNeIa remains unclear: in the single degenerate scenario they form through accumulation of mass given to the white dwarf by its companion star, while in the double degenerate scenario the explosion is caused by two white dwarfs merging. We use a population code including detailed binary star evolution to compute the time range during which SNeIa can occur after the formation of a group of stars. The code allows to differentiate between those physical scenarios and parameters which are still uncertain. These theoretical time distributions are compared to those which are observed, allowing to constrain the physical models. Using a galactic code, a comparison is also made between predictions by different models and the observed metallicity distribution of G-type dwarfs in the solar neighborhood. Because of their very long lifetime, the iron content of these stars is a good indicator of the chemical history, which is critically affected by the rate of SNeIa. We find that neither observation can be theoretically reproduced by the single degenerate scenario alone. The double degenerate one, or especially both scenarios combined, does result in fair agreement, also yielding more knowledge about the exact evolution leading to SNeIa. Including more detailed descriptions of the effects rotation has on the evolution of stars may further close the remaining gap between theory and observation.