DETONATIONS IN SUB-CHANDRASEKHAR-MASS C+O WHITE DWARFS

Abstract

Explosions of sub-Chandrasekhar-mass white dwarfs are one alternative to the\nstandard Chandrasekhar-mass model of Type Ia supernovae. They are interesting\nsince binary systems with sub-Chandrasekhar-mass primary white dwarfs should be\ncommon and this scenario would suggest a simple physical parameter which\ndetermines the explosion brightness, namely the mass of the exploding white\ndwarf. Here we perform one-dimensional hydrodynamical simulations, associated\npost-processing nucleosynthesis and multi-wavelength radiation transport\ncalculations for pure detonations of carbon-oxygen white dwarfs. The light\ncurves and spectra we obtain from these simulations are in good agreement with\nobserved properties of Type Ia supernovae. In particular, for white dwarf\nmasses from 0.97 - 1.15 Msun we obtain 56Ni masses between 0.3 and 0.8 Msun,\nsufficient to capture almost the complete range of Type Ia supernova\nbrightnesses. Our optical light curve rise times, peak colours and decline\ntimescales display trends which are generally consistent with observed\ncharacteristics although the range of B-band decline timescales displayed by\nour current set of models is somewhat too narrow. In agreement with\nobservations, the maximum light spectra of the models show clear features\nassociated with intermediate mass elements and reproduce the sense of the\nobserved correlation between explosion luminosity and the ratio of the Si II\nlines at 6355 and 5972 Angstroms. We therefore suggest that sub-Chandrasekhar\nmass explosions are a viable model for Type Ia supernovae for any binary\nevolution scenario leading to explosions in which the optical display is\ndominated by the material produced in a detonation of the primary white dwarf.\n