Interacting Binaries

Interacting binaries usually contain a compact object and a companion star. The companions are observed in various stages of evolution and have different masses. Here in Madison, building on a long tradition of studies of stellar nebulae and outflows, we have been very active in studying white dwarf close binaries. We are especially (but not only) interested in those undergoing nuclear burning in the hydrogen or helium rich envelope they accrete from  their secondary star.

When the white dwarf is "rejuvenated" by accretion it can undergo thermonuclear burning of hydrogen with the very rapid CNO cycle, that leads to a violent ejection of the accreted layers. Then the NOVA phenomenon follows, with the ejection of a mass as high as 1/10000 the solar mass in the interstellar medium in a very fast wind, at velocities of thousands of kilometers per second.

Some interacting white dwarf binaries accreting material at a very high rate may not eject all the accreted mass, or they may not undergo the nova outburst at all. In this case they are on the path towards a violent thermonuclear supernova, or type Ia supernova, responsible for nucleosyntesis of most iron in the universe. We are trying to identify which types of the white dwarf binaries really are on this supernova path.