Special Astrophysics Seminar

White dwarf binaries, mergers, and explosions

Marten van Kerkwijk

University of Toronto

Stars in binaries often have much more exciting lives, deaths, and afterlives than single ones. I will review the especially varied possibilities involving white dwarfs, which include revival and total annihilation. The latter leads to so-called type Ia supernova explosions, for which empirical calibrations of their luminosities have allowed the measurement of the acceleration of the expansion of the Universe. The standard theoretical picture, in which unstable fusion is ignited in white dwarfs that approach or are made to exceed the largest possible (Chandrasekhar) mass, can easily reproduce neither the rates nor the properties of type Ia supernovae. I will suggest that this type of ignition instead results in rarer, pure deflagration explosions, and that type Ia supernovae are produced in mergers of similar-mass carbon-oxygen white dwarfs.