New Evolutionary Channels to Type Ia Supernovae

Abstract

I review our two binary systems for promising channels to Type Ia supernovae : one is a supersoft X-ray source binary system consisting of a white dwarf and a near main-sequence star that fills the Roche lobe. The other is a symbiotic binary system consisting of a white dwarf and a low mass red-giant that fills the Roche lobe. In the both channels, strong winds from accreting white dwarfs play a key role in the way that white dwarfs grow in mass to the Chandrasekhar mass limit and explode as a Type Ia supernova. It is found that white dwarfs in recurrent novae are as massive as the Chandrasekhar mass limit and are now growing in mass. Therefore, many of the recurrent novae are immediate progenitors of Type Ia supernovae, corresponding to our two binary systems just before a Type Ia supernova explosion. We have also identified two objects in the strong wind phase of mass accreting white dwarfs : RX J0513.9-6951 in the Large Magellanic Cloud and V Sge in the Galaxy. These findings strongly support our two channels to Type Ia supernovae.