The Realizability of the Double-Detonation Mechanism for Type Ia Supernovae

University Of Alabama Tuscaloosa, Tuscaloosa AL

Investigators

Abstract

Type Ia supernovae (SN) play an essential role in measuring the accelerating expansion of the Universe, produce half of the Universe’s heavy metals, and serve as testbeds for stellar hydrodynamics, nuclear physics, binary stellar evolution, and many other aspects of astrophysics. However, despite their importance and several decades of observational and theoretical investigation, the detailed nature of the stellar systems that give rise to these explosions remains uncertain. A research team at the University of Alabama Tuscaloosa will use computer-based numerical simulations to investigate one of the most promising candidate scenarios for a SN Ia explosion. This scenario, called the “double-detonation” mechanism, starts with an explosive helium detonation on the surface of a highly compact white dwarf star, which in turn yields a carbon-burning detonation in the core of that star. The research will involve the training of graduate and undergraduate students in high performance computing and the development of scientific software. Along with research products, this work will produce short videos of scientific results intended for a general audience, a portable planetarium program for small groups, and simple simulations of stellar explosions that can be run by students in upper-division astronomy courses. Obstacles remain to understanding the double-detonation mechanism and this work will help resolve them. The detailed mechanism of the first ignition in the helium shell of the star is still unclear, calling into question the robustness of this critical stage of the beginning of the explosion. In order for this scenario to be viable as a major contributor to SNe Ia, the ignition process must not just be possible under fine-tuning, but robust and almost universal. Secondly, based on recent simulations, it is clear that the detailed structure of the outer layers of the exploding star and the presence of the companion star are critical to determining whether the resulting supernova matches those observed. Using tailored simulations, the work will determine whether a realistic ignition and surface layer structure placed in a binary star system leads to realistic supernovae. This project is jointly funded by the Division of Astronomical Sciences and the Established Program to Stimulate Competitive Research (EPSCoR). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.