Signatures of isotopes in thermonuclear supernovae

We study the observational signatures of thermonuclear burning fronts in SNe Ia. New observations suggest that our current picture of deflagration fronts is incomplete. Likely, the initial conditions need to be modified to reduce the mixing and to bring the amount of burning in current 3-D deflagration calculations (0.5... 0.7M(circle dot)) in line with results of spherical delayed detonation models (0.2... 0.3M(circle dot)) which allow to reproduce LCs and spectra of SNe Ia. In a second part, we discuss evidence for off-center DDT transitions. As a limitation, we notice that our study is based on a few individual objects. (c) 2006 Elsevier B.V. All rights reserved.