Nucleosynthesis in he-flashes on accreting white dwarfs

We present preliminary results of investigations of He-flashes on accreting C-O white dwarfs. It is shown that for accretion rates of about a few times 10-8 to 10-7 Solar mass per year which are believed to lead finally to carbon deflagration (type I) supernovae the nucleosynthesis products are significantly different from those of hydrostatic He-burning. In particular, we find large enhancements of C. Mg and Si, together with an overproduction of certain rare isotopes of heavy elements. These results should be taken into consideration if attempts are made to model the spectra of type I supernovae. Finally, we have also computed the yields of elements and their isotopes beyond iron which are modified by neutron capture reactions during the flashes. We find that the neutron flux is not sufficient to drive a r-process mainly because 18F has no time to decay to 18O during the short duration of the flashes, but nuclei with A ≤ 70 are enhanced by factors up to 50 relative to their solar system values