EXPLOSIONS OF SUB-CHANDRASEKHAR MASS WHITE-DWARFS IN 2 DIMENSIONS

The hydrodynamics of detonations of white dwarfs, having a carbon-oxyg en core and a helium envelope, are examined in a two-dimensional geome try. Various combinations of the masses of the CO core and the overlyi ng He layer are examined. Nuclear burning is directly computed with an alpha network from C-12 to Ni-56 as a part of the hydrodynamic calcul ation. The nucleosynthesis yield is similar to that needed for Type Ia supernovae to explain the variation in alpha elements relative to iro n in Population II stars. Significant amounts of radioactive Ti-44 pro duced. The yields are similar to those predicted from one-dimensional computations, despite the very nonspherical hydrodynamic behavior. Lig ht curves are simulated and compared to observations of Type Ia supern ovae. The observed variation in peak absolute luminosity and in post-m aximum decline rate is reproduced in a natural way. A rough comparison of predicted velocities with observations of Ca II H and K, Mg II lam bda 4481 and Si II lambda 6355 in SN 1989B (in NGC 3627) is promising; implications for the use of Type Ia supernovae as distance indicators are discussed, and the key importance of spectral synthesis is stress ed.