Characterizing the local double white dwarf population

Binary systems consisting of two WDs are important in a broad range of astrophysical contexts, from stellar evolution, through Type-Ia supernova (SN Ia) progenitors, to sources of gravitational waves. SNe Ia—supernova explosions of WDs—are a major source of heavy elements, and, as ‘standard candles’, they have provided one of the fundamental methods for estimating distances in the Universe. However, the nature of the progenitor systems of SNe Ia is still unclear. A progenitor scenario that has been long considered is the double-degenerate scenario, in which a double WD binary loses energy and angular momentum to gravitational waves, until merger and possible explosion as a SN Ia. If most SN Ia explosions are the result of double WD mergers, then the observed double WD merger rate should be high enough to account for the observed SN Ia rate. This motivates us to ask: are there enough double WDs to explain the observed SN Ia rate?

A review paper:

Limiting the population of collisional triples using Gaia DR2

Limiting the population of collisional triples using Gaia DR2

The collisional-triple SN Ia progenitor model posits that SNe Ia result from head-on collisions of double WDs, driven by dynamical perturbations by the tertiary stars in mild-hierarchical triple systems. To reproduce the Galactic SN Ia rate, at least ∼30−55% of all WDs would need to be in triple systems of a specific architecture...