Session 12 - Distance Scale.
Display session, Monday, January 13
Metropolitan Ballroom,

## [12.03] Type Ia Supernovae: Influence of the Initial Metallicity/ Consequences for the Determination of qo

F. K. Thielemann (U. Basel), P. Hoeflich (U. Texas), A. Khokhlov (NRL), K. Nomoto (U. Tokyo), J. C. Wheeler (U. Texas)

The influence of mixing and the metallicity of the progenitor systems of Type Ia supernovae has been studied by detailed theoretical models at the example of a delayed detonation model with respect to the explosive nucleosynthesis, the light curves and spectra. Consequences for the use of Type Ia supernovae as distance indicators to determine the cosmological deceleration q_o are discussed. The calculations are consistent with respect to the explosion mechanism, the optical and infrared light curves, and the spectral evolution, leaving the description of the nucelar burning front and the structure of the white dwarf as the only free parameters.

The explosions are calculated using a one-dimensional Lagrangian radiation-hydro code including a nuclear network. Subsequently, the light curves are constructed. Spectra are computed for several instants of time using the density, chemical, and luminosity structure resulting from the light curve code. Our NLTE code solves the relativistic radiation transport equations in comoving frame consistently with the statistical equations and ionization due to \gamma radiation for the most important elements (C,, O, Ne, Na, Mg, Si, S, Ca, Fe, Co, Ni). Changing the initial metallicity from Population I to II alters the isotopic composition of the outer layers, namely decrease the ^54Fe production with severe consequences on the light curves and spectra. E.g. a change of the metallicity by a factor of 3 at z=0.5 alters the color index B-V by \approx 0.3^m. This may make evolutionary effects comparable to the effect of cosmic deceleration to be measured.