The production of electron-capture elements in thermonuclear supernovae: Theory vs observations

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Abstract
Type Ia supernovae explosively destroy C/O white dwarfs (WDs) in multiple stellar systems. They produce ≈50% of the iron-group elements in the universe, synthesize electron-capture (EC) elements, drive nuclear physics experiments, and underpin high-precision cosmology. To first order, the outcome is governed by nuclear physics, a property often described as “stellar amnesia.” Recently, this stellar amnesia has begun to be broken by the nearly universal detection of EC elements with James Webb Space Telescope. These elements trace high-density burning, largely ruling out the currently popular He-triggered, sub-MCh detonation models as the dominant channel. Instead, the ubiquitous presence of EC is shifting back the focus to dynamical and secular mergers and near-MCh explosions similar to the deflagration model W7, but in which the nuclear flame undergoes a deflagration-to-detonation transition. The early deflagration phase is especially important because spherical simulations identify the central WD density, and thus the WD mass, as a key parameter governing the explosion. Here, we present detailed magneto-hydrodynamical simulations. We find that small-scale, preexisting turbulence expected from the pre-explosion smoldering phase is essential for overcoming the fundamental challenges imposed by the intrinsic 3D physics. This turbulence systematically reduces the production of EC elements by about a factor of two, implying the need for WD central densities closer to those associated with accretion-induced collapse to a neutron star. We also demonstrate the effect of magnetic fields near the saturation field strength and highlight the need for higher-precision EC rates at low Ye.
Funding Information
  • NASA grant JWST-GO-02114
  • NASA grant JWST-GO-02122
  • NASA grant JWST-GO-04522
  • NASA grant JWST-GO-04217
  • NASA grant JWST-GO-04436
  • NASA grant JWST-GO-03726
  • NASA grant JWST-GO-05057
  • NASA grant JWST-GO-05290
  • NASA grant JWST-GO-06023
  • NASA grant JWST-GO-06677
  • NASA grant JWST-GO-06213
  • NASA grant JWST-GO-06583
  • NASA grant JWST-GO-09231

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