On Type Ia supernovae from the collisions of two white dwarfs

We explore collisions between two white dwarfs as a pathway for making Type Ia supernovae (SNIa). White dwarf number densities in globular clusters allow 10–100, redshift ≲1 collisions per year, and observations by Chomiuk et al. of globular clusters in the nearby S0 galaxy NGC 7457 have detected what is likely to be a SNIa remnant. We carry out simulations of the collision between two 0.6M⊙ white dwarfs at various impact parameters and mass resolutions. For impact parameters less than half the radius of the white dwarf, we find such collisions produce ≈0.4M⊙ of56Ni, making such events potential candidates for underluminous SNIa or a new class of transients between Novae and SNIa.