Speaker: Michael Tucker (University of Hawai'i)
How White Dwarfs Explode as Type Ia Supernovae
Type Ia supernovae are crucial aspects of observational cosmology and galactic chemical evolution yet the astronomical community still lacks a genuine understanding of their origins. These explosions arise from white dwarf stars in binary systems but that is where the consensus ends. However, over the past few years we have finally realized for the majority of Type Ia supernovae that the companion cannot be a non-degenerate star experiencing Roche Lobe overflow as the myriad of predicted observational signatures repeatedly fail to materialize. This suggests that the companion must be another degenerate star. However, new questions arise about how the double white dwarf system explodes as a Type Ia supernova. Do both white dwarfs have carbon/oxygen cores or is one of them a low-mass He white dwarf? Is the exploding white dwarf near the Chandrasekar mass? What triggers the explosion and how does the flame propagate through the star? Answers to these questions are needed to understand how the progenitors, explosions, and resulting nucleosynthesis evolve with redshift. But, observational signatures of double-degenerate systems are subtle. I will detail my first-of-its-kind measurement directly probing the density of the exploding star for the bright and nearby SN Ia 2011fe which uniquely constrains the progenitor system. However, this was an unprecedented opportunity and other observational tests are required. I will conclude by detailing a new technique for measuring explosion symmetry which will discern the origin of these cosmic signposts in the next few years.
