2018MNRAS.480.3702B

We examine catalogues of white dwarfs (WDs) and we find that there is a sufficient number of massive WDs (i.e. M_WD_ ≳1.35 M_☉) that might potentially explode as Type Ia supernovae (SNe Ia) in the context of the core-degenerate scenario. In the core-degenerate scenario, a WD merges with the carbon-oxygen core of a giant star, and these form a massive WD that might explode with a time delay of years to billions of years. If the core-degenerate scenario accounts for all SNe Ia, then we calculate that about 0.2 per cent of the present WDs in the Galaxy are massive. Furthermore, we find from the catalogues that the fraction of massive WDs relative to all WDs is about 1-3 per cent, with large uncertainties (i.e. five to ten times the required number). If there are many SNe Ia that result from lower-mass WDs (i.e. M_WD_ ≲1.3 M_☉), for which another scenario is responsible, and if the core-degenerate scenario accounts only for the SNe Ia that explode as massive WDs, then the ratio of observed massive WDs to required is even larger. Although there are several unresolved difficulties regarding the core-degenerate scenario, it is our view that this finding leaves the core-degenerate scenario as a possible SN Ia scenario, and possibly even a promising SN Ia scenario.