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Title: Chandrasekhar-mass or sub-Chandrasekhar-mass white dwarfs in normal Type Ia supernovae
Plain: The exploding white dwarf may be close to the maximum mass a white dwarf can have (about 1.4 Suns), or lighter, with a helium layer on its surface detonating first and setting off the core. Each picture predicts different elements in the debris.
Precise: For normal SNe Ia, decide whether the exploding white dwarf is near $M_{\mathrm{Ch}} = 1.38\,M_{\mathrm{sun}}$ with a deflagration-to-detonation transition, or at $0.9\ \text{to}\ 1.1\,M_{\mathrm{sun}}$ exploding by a helium-shell detonation that triggers a carbon-oxygen core detonation (double detonation), and give the fraction of each. Discriminating observables include $\mathrm{Mn}/\mathrm{Fe}$ and stable $\mathrm{Ni}/\mathrm{Fe}$ in ejecta and nebular spectra, the stratification of Ca and other intermediate-mass elements in young remnants, and early-time spectra.
Settled by: Nebular-phase stable Ni and Mn yields and remnant element stratification for a statistical sample, compared with 3D explosion models of both classes.
Kind: well-posed
Answer type: classification
References: (empty)
Literature status: contested
Status note: In 2025 a double calcium shell in the young Large Magellanic Cloud remnant SNR 0509-67.5 was reported as the predicted signature of a double detonation (Das et al., Nature Astronomy, 2025); whether this is the common route remains open.
Posed since: (empty)