Philipp Podsiadlowski

Abstract:

In the last ten years it has becomes increasingly clear that the progenitor of SN 1987A must have experienced a dramatic event some 20,000 yr before the explosion, most likely the merger with a companion star. We here present recent detailed models of such a merger event, using stellar and 2-d hydrodynamical simulations of the various phases in the evolution of the progenitor. We show that in the final merging phase, a stream emanating from the embedded companion star can penetrate deep into the helium core of the progenitor; this leads to the dredge-up of helium and some unusual nucleosynthesis. This can explain most of the major anomalies of the progenitor, its blue colour, the main chemical anomalies in the envelope and the inner ring of the triple-ring nebula: Our simulations suggest that the core of the progenitor should have been rapidly rotating at the time of the explosion which may have affected the explosion and may be responsible for some of the observed asymmetries in the ejecta.

Abstract:

Using binary population synthesis (BPS), we studied the birthrates of SNe Ia for two progenitor models - the single degenerate model and the double degenerate model. We find that the birthrates from both models are within a factor of a few comparable to those inferred observationally. For each model, we investigate different star-formation histories (single star burst or constant star formation), different metallicities (Z = 0.02, 0.004, 0.001), different parameters for the BPS model (mass transfer efficiency during stable mass transfer, common-envelope ejection parameters) and obtain the evolution of birthrates with time.