SN Ia-CSM 2020aeuh: Massive binary C/O WD merger?

Abstract

I explore the origin of the circumstellar (CS) shell of the unusual SN Ia 2020aeuh based on the light curve model abd observational constraints. I estimate the ${}^{56}$Ni mass ($1.1M\odot$), CS shell mass ($0.04-0.2M\odot$), radius ($2\times 10^{16}$ cm), and expansion velocity $\lesssim 200$ km/s. Large ${}^{56}$Ni mass and properties of the CS shell are consistent with the scenario of massive binary white dwarf merger that has been accompanied with the ejection of $\sim 0.1M\odot$ of matter. It is argued that SN~2020aeuh exploded not earlier than 30 yr after the merger.