Seeking for the Progenitors of Type Ia Supernovae

Abstract

Type Ia supernovae are thought to be thermonuclear explosions of accreting white dwarfs that reach a critical mass limit. Despite their importance as cosmological distance indicators, the nature of their progenitors has remained controversial. Observations carried out by our team with VLT-UVES led us to the detection of circumstellar material in a normal Type Ia supernova. The expansion velocities, densities and dimensions of the circumstellar envelope indicate that this material was ejected from the system prior to the explosion. The relatively low expansion velocities appear to favour a progenitor system where a white dwarf accretes material from a companion star which is in the red-giant phase at the time of the explosion.