Double detonations: variations in Type Ia supernovae due to different core and He shell masses -- II: synthetic observables

TL;DR

This study uses 3D radiative transfer simulations to explore how variations in core and helium shell masses in double detonation models of sub-Chandrasekhar white dwarfs affect observable properties of Type Ia supernovae, highlighting challenges in matching normal SNe Ia colors.

Contribution

It provides detailed 3D synthetic observables for a range of double detonation models, emphasizing spectral features and color discrepancies with normal SNe Ia.

Findings

Models reproduce faint end of width-luminosity relation

All models show extremely red colors not observed in normal SNe Ia

Spectral features suggest classification as peculiar SNe Ia

Abstract

Double detonations of sub-Chandrasekhar mass white dwarfs are a promising explosion scenario for Type Ia supernovae, whereby a detonation in a surface helium shell triggers a secondary detonation in a carbon-oxygen core. Recent work has shown that low mass helium shell models reproduce observations of normal SNe Ia. We present 3D radiative transfer simulations for a suite of 3D simulations of the double detonation explosion scenario for a range of shell and core masses. We find light curves broadly able to reproduce the faint end of the width-luminosity relation shown by SNe Ia, however, we find that all of our models show extremely red colours, not observed in normal SNe Ia. This includes our lowest mass helium shell model. We find clear Ti II absorption features in the model spectra, which would lead to classification as peculiar SNe Ia, as well as line blanketing in some lines of sight by singly ionised Cr and Fe-peak elements. Our radiative transfer simulations show that these explosion models remain promising to explain peculiar SNe Ia. Future full non-LTE simulations may improve the agreement of these explosion models with observations of normal SNe Ia.