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oai:figshare.com:article/32826197 2026-10-01T16:10:04Z portal_1172 item_type_8 month_year_10_2026

Exploring the origins of Type Ia supernovae with Monte Carlo radiative transfer Joshua Mark Pollin (24304463) PUREID: 663734972 Supernovae type Ia white dwarf radiative transfer MCRT numerical methods Dynamically-driven double-degenerate double-detonation Type Ia supernovae (SNe la) are extremely energetic astrophysical phenomena. However, key questions surrounding their progenitors remain unanswered. The double-degenerate scenario has been heavily favoured in recent years, with the double-detonation of a sub-Chandrasekhar mass white dwarf (WD) being extensively studied. In this scenario, a carbon-oxygen WD accretes helium from a companion and undergoes a shell detonation, subsequently igniting a core detonation. Observational evidence suggests some WDs originate from a system where a primary WD has undergone a double-detonation, referred to as the OneExpl scenario. Recent evidence suggests the secondary WD may also be disrupted during the merger and detonate, referred to as the TwoExpl scenario. In both scenarios, there are substantial departures from spherical symmetry. To constrain the viability of either scenario and understand the asymmetries, we have computed 3D photospheric- and 3D nebular-phase synthetic observables. At times around maximum light, the observable properties are comparable in both scenarios and resemble those of peculiar SNe la. At late times, we find that the multidimensional structure of the models has a considerable influence on the overall ionisation balance and the width, velocity, and morphology of spectral features, which are sensitive to the observer's orientation. In the TwoExpl scenario, profiles such as the 8.991µm Ar III feature can appear somewhat flat-topped from some orientations and centrally peaked from others. Consequently, the current realisation of the OneExpl model represents a more plausible match to normal SNe la. Our investigations demonstrate that the multidimensional structure of the explosion models is crucial for reconciling models with observational data. Further model realisations and space-based observations are needed to determine if either pathway is responsible for normal SNe la. 2026-10-01T16:10:04Z Text Thesis 10.17034/32826197.v1 https://figshare.com/articles/thesis/Exploring_the_origins_of_Type_Ia_supernovae_with_Monte_Carlo_radiative_transfer/32826197 All Rights Reserved