Oxygen-neon-rich merger during common envelope evolution

We conduct a population synthesis study of the common envelope evolution (CEE) of a white dwarf (WD) and an asymptotic giant branch (AGB) star and find that the potential number of type Ia supernovae (SNe Ia) from the core degenerate (CD) and from the double degenerate (DD) scenarios are of the same order of magnitude. For the CD scenario, we consider cases where a carbon-oxygen-rich (CO) AGB core and a CO WD merge during the CEE and leave a WD remnant with a mass of M_WD ≥ 1.35M_⊙, and for the DD scenario we count surviving CO WD binary systems that merge within a time of 10¹⁰ yr. When either the AGB core or the WD are oxygen neon rich (ONe) we assume that the outcome might be a peculiar SN Ia. We find that the number of potential peculiar SNe Ia in the channels we study, which do not include peculiar SNe Ia that involve helium WDs or helium donors, are non-negligible, but less than the number of normal SNe Ia. If an SN Ia or a peculiar SN Ia explosion takes place within about million years after CEE, whether in the CD scenario or in the DD scenario, a massive circumstellar matter is present at explosion time. Our results are compatible with the suggestion that Chandrasekhar-mass SNe Ia mostly come from the CD scenario, and sub-Chandrasekhar SNe Ia mostly come from the DD scenario.