title: Sub-luminous type Ia supernovae from the mergers of equal-mass white dwarfs with mass approximately 0.9M[symbol: see text].
abstract: Type Ia supernovae are thought to result from thermonuclear explosions of carbon-oxygen white dwarf stars. Existing models generally explain the observed properties, with the exception of the sub-luminous 1991bg-like supernovae. It has long been suspected that the merger of two white dwarfs could give rise to a type Ia event, but hitherto simulations have failed to produce an explosion. Here we report a simulation of the merger of two equal-mass white dwarfs that leads to a sub-luminous explosion, although at the expense of requiring a single common-envelope phase, and component masses of approximately 0.9M[symbol: see text]. The light curve is too broad, but the synthesized spectra, red colour and low expansion velocities are all close to what is observed for sub-luminous 1991bg-like events. Although the mass ratios can be slightly less than one and still produce a sub-luminous event, the masses have to be in the range 0.83M[symbol: see text] to 0.9M[symbol: see text].
authors.affiliation: Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Strasse 1, 85748 Garching, Germany. rpakmor@mpa-garching.mpg.de
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Pakmor
authors.forename: Markus
authors.initials: M
authors.lastname: Kromer
authors.forename: Friedrich K
authors.initials: FK
authors.lastname: Röpke
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Sim
authors.forename: Ashley J
authors.initials: AJ
authors.lastname: Ruiter
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hillebrandt