From Deflagration to Detonation: Understanding Type Ia Supernova Explosions

Background: Type Ia supernovae (SNe Ia) are primarily understood through Chandrasekhar mass (M𝐶ℎ) models; however, the pure deflagration (subsonic burning front) and pure detonation (supersonic) fail to replicate the observed distribution of 56Ni and intermediate mass elements. Objectives: We critically review the integrated delayed detonation model (DelDetM) in light of the latest observations and numerical simulations. Method: This review analyzes recent developments in modeling and simulations of SNe Ia explosions, focusing on near M𝐶ℎ delayed detonation and sub-Chandrasekhar mass doubledetonation mechanisms. The models are compared against the latest observational constraints obtained from multi-wavelength photometry and nebular phase spectroscopy. We focus on the contrast between various ignition conditions, the underlying physics of detonation triggers, and the yields of nuclear reactions. Findings: Pure deflagration models provide insufficient explosion energy (∼ 0.6 − 0.8 × 1051 erg) and leave substantial unburned C-O, while pure detonation overproduces IMEs. DelDetM provides adequate 56Ni mass (0.4 − 0.8 M􀀀) and layered ejecta structures consistent with recent observations. 3-D simulations highlight the critical role of turbulence and flame instabilities in determining deflagration-to-detonation transition, while JWST observations provide new infrared constraints on ejecta stratification. The doubledetonation model further explains the observed diversity in SNe Ia. Properly tuned DelDetM can successfully explain spectra, light curves, and nucleosynthesis yields. However, 3D simulations remain challenging due to uncertainties in the transition mechanism, excess unburned material, and imperfect chemical stratification. The competing double detonation model with a thin shell also matches nucleosynthesis yields of normal SNe Ia. Insufficient understanding of progenitor evolution and the difficulty in modeling turbulence and combustion across vast scales in multidimensional simulations have been identified as major bottlenecks. Significance: This article integrates the latest results from computer simulations and observations and provides a precise roadmap for future research on the physical mechanisms underlying the thermonuclear runaway in SNe Ia. Keywords: Delayed Detonation; Type Ia Supernovae; White Dwarfs; Hydrodynamical Simulations; Nucleosynthesis; Chandrasekhar Mass; Double Detonation