Illuminating Mergers of Carbon-Oxygen White Dwarfs and Their Possible Link to Thermonuclear Supernovae

The merger of two carbon-oxygen white dwarfs (CO WDs) can either create a more massive WD, lead to collapse into a neutron star, or explode spectacularly as a thermonuclear, or Type Ia, supernova (SN Ia). It has traditionally been believed that SNe Ia result only from mergers at or above the Chandrasekhar mass (MCh), as these can subsequently become dense enough to trigger runaway fusion. Recently, however, it has been proposed that the merged product, or "remnant", might instead subsequently ignite fusion from high temperatures. This opens the possibility of SNe Ia arising even from sub-MCh mergers. To investigate this, I conducted a series of hydrodynamic simulations of the merging process. I first performed simulations spanning the range of possible mergers using the smoothed-particle hydrodynamics code Gasoline, finding that remnant configurations are roughly homologous for mergers of WDs with the same difference in mass ∆M. In particular, "similar-mass" mergers with ∆MPh.D