SN Ia CSM 2020aeuh: A Massive Binary C/O White Dwarf Merger?

The origin of the circumstellar (CS) shell of the unusual SN Ia 2020aeuh is explored using a light curve model and observational constraints. The synthesized $${}^{56}$$ Ni mass ( $${\approx}1$$ $$M_{\odot}$$ ), the mass of the CS shell (0.04–0.2 $$M_{\odot}$$ ), the radius ( $$2\times 10^{16}$$ cm), and its expansion velocity ( $${\lesssim}200$$ km s $${}^{-1}$$ ) have been estimated. The large $${}^{56}$$ Ni mass and the properties of the CS shell are consistent with the scenario of a massive binary C/O white dwarf merger that was accompanied by the loss of $${\sim}0.1$$ $$M_{\odot}$$ of matter. The supernova is shown to have exploded $${\gtrsim}30$$ years after the white dwarf merger.