It's always the quiet ones: Single Degenerate Double Detonation Type Ia Supernova from Quiescent Helium Accretion

TL;DR

This study models a sub-Chandrasekhar mass white dwarf accreting helium, demonstrating that quiet, long-term accretion can lead to double detonations producing normal Type Ia supernovae with realistic yields and velocities.

Contribution

It presents a detailed multi-dimensional simulation showing how quiescent helium accretion can trigger double detonations in white dwarfs, supporting their role as Type Ia supernova progenitors.

Findings

Ni56 yield of ~0.64 solar masses

Ejecta velocities up to 22,000 km/s

Consistent with normal Type Ia supernovae

Abstract

We investigate a sub-Chandrasekhar mass double detonation pathway for Type Ia supernovae arising from single degenerate helium accreting carbon-oxygen white dwarfs. Building on our previous one dimensional study of recurrent helium novae (Hillman et al. 2025), we evolve a 0.7 solar mass white dwarf through steady accretion at 10^-8 Msun yr^-1 until it reaches 1.1 solar mass, yielding realistic, time evolved helium rich profiles. These profiles are mapped into FLASH simulations, incorporating nuclear burning for helium and carbon-oxygen detonation, in multi-dimensional hydrodynamic runs. A localized, modest temperature perturbation near the base of the helium shell robustly triggers an outward helium-shell detonation. The ensuing inward propagating shock converges in the carbon-oxygen core, igniting a secondary detonation that unbinds the star. We obtain a Ni56 yield of ~0.64 solar mass, an intermediate-mass element (Si-Ca) mass of ~0.41 solar mass, and maximum ejecta velocities approaching 22,000 km/s, values consistent with normal Type Ia supernovae. Our results demonstrate that recurrent helium accretors, typically quiescent over long timescales, can evolve under subtle, "quiet" conditions to trigger robust double detonations, supporting their role as viable progenitors of sub-Chandrasekhar mass Type Ia supernovae.