Interacting binary star

The physical conditions in such a system can be complex and highly variable, and they are common sources of cataclysmic outbursts.

If the compact object is a white dwarf, then accretion of material from the evolved star onto the white dwarf's surface may result in its mass increasing to beyond the Chandrasekhar limit.

This can lead to runaway thermonuclear reactions and the massive explosion of the star in a Type I supernova.

[1] In close binary systems where the first Roche lobe overflow of the primary occurs prior to helium flash, the shedding of mass can leave behind a helium white dwarf with a mass as low as 0.1 M☉.

Evolutionary models of binaries suggest that a majority of such closely orbiting white dwarf companions will be helium–based.

Artist's impression of a low-mass X-ray binary (LMXB): an evolved low-mass yellow sub-giant star transfers mass to a neutron star . Because the accretor is a compact object, an accretion disc forms, which is the source of the X-rays . Source .