"Typing thermonuclear explosions from observations of young supernova remnants"

Résumé

Type Ia supernovae (SNe) are believed to mark the thermonuclear explosion of a white dwarf (WD). Despite their importance in cosmology, their progenitor system and explosion mechanism are still unclear. Igniting a WD requires some interaction, a major question being whether one WD (single degenerate) or two WDs (double degenerate) are involved. Another theoretical interrogation is whether the exploding WD is close to the Chandrasekhar mass limit, or well below it.
Young supernova remnants (SNRs) can be used as a probe of the explosion physics. In particular a variety of diagnostics are available from X-ray observations of the shocked plasma. Recent progress in the simulation of SNe has shown the importance of turbulence and asymmetries in successful explosions, which prompts us to revisit the subsequent phase, the SNR phase. Can we use the SNR morphology as a probe of the explosion mechanism?
Our SN2SNR project targets the thermonuclear case and makes the connection between the explosion physics and the remnant dynamics. We have run 3D simulations of a SNR starting from the output of state-of-the-art 3D SN simulations. We started with the N100 model, the canonical case of an accreting Chandrasekhar-mass WD that is undergoing a delayed detonation. By analyzing the wavefronts we quantified the imprint of the explosion on the remnant over time. Assuming a uniform ambient medium, we found that the impact of the SN on the SNR may still be visible after hundreds of years. We then performed a first comparative study of variants of this explosion model, in terms of the ignition pattern (N5 vs N100) and the propagation of the flame (deflagration vs detonation), which bear different levels of asymmetry. Lastly we investigated a different kind of model, where a sub-Chandrasekhar mass primary WD explodes via a double detonation while the secondary WD survives and is ejected away. This scenario has been called a “dynamically-driven double-degenerate double-detonation” or D^6. Our simulations again reveal specific signatures of the progenitor system and explosion mechanism, in particular a large and long-lasting conical shadow in the ejecta.
Our ongoing work shows the intrinsic diversity of thermonuclear SNe and their remnants, and offers new perspectives for the interpretation of observations of young SNRs.