Coalescence of two dwarf white

The principal virtues of this type of models are the natural absence of hydrogen and helium in the spectrum, abundances comparable with the rate of supernovæ and a natural explanation for a family of objects to a parameter (the sum of the masses of two the dwarf white ones). The progéniteurs exist in an attested way and must give place to coalescence by radiation of gravitational waves. Therefore, there is a violent phenomenon which accompanies it even if it is not a supernova of the Ia type.

After coalescence, there is formation of an accretion disc around most massive of two the dwarf white ones formed of the matter of the least massive. In the case of an accretion rate of $10^{-6 } \rm \, M_\odot añ{-1}$, a lighting out-heart causes a propagation of flame towards the interior which converts the heart into O/Ne/Mg. This configuration is unstable by orbital electron capture on $^{24}Mg$ causing a gravitational collapse which transforms the dwarf white one into neutron star.

Studies on turbulent viscosity due to magnetohydrodynamic instabilities suggest that it is very difficult to avoid so large accretion rates.

Another possibility to avoid gravitational collapse, would be to rather initiate the combustion of carbon by a detonation than a deflagration.

This type of progenitor could account for the very luminous objects like 1991T.