Exploring the Carbon Simmering Phase: Reaction Rates, Mixing, and the Convective Urca Process

Abstract

The neutron excess at the time of explosion provides a powerful discriminant among models of Type Ia supernovae. Recent calculations of the carbon simmering phase in single degenerate progenitors have disagreed about the final neutron excess. We find that the treatment of mixing in convection zones likely contributes to the difference. We demonstrate that in MESA models, heating from exothermic weak reactions plays a significant role in raising the temperature of the WD. This emphasizes the important role that the convective Urca process plays during simmering. We briefly summarize the shortcomings of current models during this phase. Ultimately, we do not pinpoint the difference between the results reported in the literature, but show that the results are consistent with different net energetics of the convective Urca process. This problem serves as an important motivation for the development of models of the convective Urca process suitable for incorporation into stellar evolution codes.

10 pages, 7 figures; Accepted to ApJ

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Cited by in corpus (7)

• Stable nickel production in Type Ia supernovae: A smoking gun for the progenitor mass?
• Urca Cooling in Neutron Star Crusts and Oceans: Effects of Nuclear Excitations
• Hydrodynamic Simulations of Electron-capture Supernovae: Progenitor and Dimension Dependence
• Pre-explosive accretion and simmering phases of Type Ia Supernovae
• 3D Convective Urca Process in a Simmering White Dwarf
• Sensitivity of 3D Convective Urca Simulations to Changes in Urca Reactions
• On the Importance of the Convective Urca Process in 3D Simulations of a Simmering White Dwarf