Sub-Chandrasekhar Mass Models for Type IA Supernovae: Single and Multipoint Ignition

Abstract

The name of Sub-Chandrasekhar mass models for Type Ia Supernovae has been recently coined to design those white dwarfs with masses well below 1.4M⊙ which through off-center explosive helium ignition and further induced carbon detonation, could become a bright Supernova belonging to the remarkably homogeneous class known as Type la Supernovae. The scenario usually invoked consists of a massively moderate carbon-oxygen white dwarf accreting matter from a companion. As a consequence of the accretion process a thick layer of helium of 0.15–0.25M⊙ settles and later ignites on top of a 0.6–0.9M⊙ C-O white dwarf. A hydrodynamical stage begins characterized by: 1) formation of a steady Chapman-Jouguet detonation, 2) transformation of the He layer in Fe-peak elements moving faster 10000 km s¯1, 3) induced ignition of the C-O core, and formation of a steady carbon detonation wave, 4) incineration of the core and formation of more Fe-peak and intermediate mass (Si-Ti) elements, 5) destruction of the star in the hydrodynamical time, giving rise to the optical display typical of Type Ia supernovae explosions.