Unveiling the origins of white-dwarf explosions

Introduction

The explosive deaths of white dwarfs are essential in heavy element nucleosynthesis, galaxy feedback, and for understanding the evolution of binary systems. Type Ia supernovae (SNe Ia) are famous for their key role as cosmological-distance indicators and in the discovery of the accelerating Universe.

Recent Developments

Recent high-cadence surveys and theoretical advances have hinted that SNe Ia may not be the dominant way in which white dwarfs explode. There is a potential existence of large populations of faint and rapidly evolving white-dwarf explosions.

Exotic Transients

These unexplored classes of exotic transients may come from:

• White dwarfs being torn apart by intermediate-mass black holes
• Mergers with neutron stars
• Collisions in triple systems

However, the mapping between explosions and observed transients is undetermined.

Project Aims

This project aims at providing the first complete census of the multiple ways that white dwarfs explode by mapping their observations to their explosion physics and constraining their diversity.

Importance of the Sample

This sample will be crucial for:

1. Defining optimal samples of SNe Ia for cosmology
2. Determining the rates and contributions of white-dwarf explosions to the origin of the elements

Methodology

We will achieve this by: i) Obtaining the largest ever, rapidly discovered and spectroscopically confirmed sample of white-dwarf transients with detailed follow-up observations.
ii) Applying machine-learning techniques (e.g., neural-network emulators) for rapid comparison to sophisticated explosion models.
iii) Determining the rates and diversity of their explosions in different galaxy environments.

Implications

The confirmation and exploration of the multiple explosion channels for producing normal SNe Ia and exotic white-dwarf transients will have major implications for:

• Their nucleosynthetic yields
• Their use in cosmology
• Predicting rates of double white dwarfs that will be detected in huge numbers in the Milky Way by the gravitational-wave detector, LISA.