STellar Astrophysics & Relativity research cluster/Physics Department seminar
TYPE Ia SUPERNOVAE AND THE DOUBLE CORE COMMON ENVELOPE SCENARIO
Eric Blais
Physics Department,
Bishop’s University
Friday, March 11, 2011
1:30 – 2:30 p.m.
Nicolls 315
Supernovae are incredibly energetic explosions of massive stars that have reached the end of their lives. Type Ia supernovae (SN Ia) are special in that they can be used by astronomers to establish a scale of distances in the Universe. Despite their importance, we have yet to conclusively determine their origins. While we know that they come from the detonation of white dwarfs (the dense cores of dead stars) and that this detonation requires the white dwarf to accrete mass from a companion star, it still remains a mystery how this process actually occurs. SN Ia progenitors are therefore a very active area of research. However, none of the scenarios currently proposed in the literature provide satisfactory explanations for their origin. We propose a new method for creating double degenerate systems (systems containing two white dwarfs) which can merge to form SN Ia. This relies on stars of very similar masses being born in a binary system and evolving to the giant stage at the same time. If the stars are close enough, this can lead to a common envelope event, where the cores of the two stars spiral in together in a common envelope, releasing enough energy to expel it into space, leaving only two white dwarfs behind. This scenario can account for a substantial proportion of observed SN Ia, and can complement another formation scenario to account for the full population. This model agrees very well with observations made on the delay time distribution of SN Ia.
