Modelling Turbulent Deflagrations in Type Ia Supernovae J.C. Niemeyer a , W. Schmidt a and C. Klingenberg b a Institut f¨ ur Theoretische Physik und Astrophysik, Universit¨ at W¨ urzburg Am Hubland, D-97074 W¨ urzburg, Germany b Institut f¨ ur Angewandte Mathematik und Statistik, Universit¨ at W¨ urzburg Am Hubland, D-97074 W¨ urzburg, Germany We present an overview of the current state of multidimensional modelling of type Ia supernovae and an example for surprising consequences of impoving the physics of the model. In this case, an improved handling of subgrid scale turbulence gives rise to lower burning rates and a decreased global energy release. While this result is too preliminary to be interpreted quantitatively, it shows that much work remains to be done before the turbulent deflagration model can be declared to be understood and/or insufficient to explain normal type Ia supernovae. 1. INTRODUCTION Type Ia supernovae (SNe Ia) have received a lot of attention recently in their roles as cosmological distance indicators and prime witnesses of the accelerated expansion of the universe (see [1,2] for reviews). Apart from cosmology, there is an urgent need for reliable SN Ia models in the context of nucleosynthesis of heavy elements and galactic chemical evolution. Yet despite more than three decades of research we are still debating some fundamental aspects of the physics of the stellar explosions that give rise to these bright and powerful events. As is widely known, the most successful model for a SN Ia is the thermonuclear explosion of a CO-White Dwarf driven to criticallity by accretion in a binary system until it reaches the Chandrasekhar mass (e.g., [3]). “Successful” means that in principle, as demonstrated by spherically symmetric explosion models, the right amounts of 56 Ni and intermediate mass elements can be produced (with adequate velocities) to explain the light curves and spectra of typical SNe Ia. Unfortunately, in these models much of the essential explosion physics is hidden in the parametrization of the thermonuclear burning speed. In the case of the initial subsonic deflagration phase, the speed is basically a free parameter whereas for the proposed secondary phase of a delayed detonation [4,5], the speed is fixed by hydrodynamics but the onset of the detonation is dialed in by hand. Furthermore, in the latter case the non-spherical geometry of an off-center detonation cannot be captured in 1D-simulations. Much progress has been made recently in the field of multidimensional (2 and 3D) sim- ulations of SN Ia explosions [6–8]. Parameter studies with 3D simulations of the turbulent Nuclear Physics A 758 (2005) 431c–438c 0375-9474/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nuclphysa.2005.05.080