A comparison of the evolution of white dwarfs in interacting low mass and in high mass binaries

Most stars become white dwarfs, and a large fraction of all stars (depending on mass range) are in binary systems. A few percents of stars with mass lower than about 2 solar masses become interacting binaries, in which a white dwarf interacts with the companion, accreting mass and, almost always, triggering nuclear fusion near the white dwarf surface. The fractions of interacting binaries may be much larger, perhaps even close to 50%, for white dwarfs originating from stars that had a mass above about 2 solar masses. While at lower masses we know that accreting white dwarfs often undergo thermonuclear runaway and loose mass in nova outbursts, the fate of massive white dwarfs with massive companions is not known yet. In this talk, I will illustrate what we know about accreting and hydrogen burning white dwarfs along the HR diagram, through what we have learned from the observations of supersoft X-ray sources. I will also discuss the implications for the progenitors of thermonuclear supernovae, and even possible consequences for the rate of core collapse supernovae.