Ransome, C (2023) Using the environments of type IIn supernovae and classical novae to constrain progenitor properties. Doctoral thesis, LJMU.

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Abstract

Supernovae are the explosive death of stars. Massive stars (M>8M⊙) end their lives as core-collapse supernovae. A white dwarf that gains mass and reaches the Chandrasekhar mass (∼1.4M⊙) explodes as a thermonuclear supernova. Supernovae can be broadly split into two classes based on whether hydrogen is present in the spectrum. Type I supernovae lack hydrogen and type II supernovae exhibit hydrogen.
Type IIn supernovae are a mysterious subclass, they are highly inhomogeneous and are characterised by complex Balmer line profiles with a narrow component which is interpreted as interaction between the SN ejecta and a dense, pre-existing hydrogen-rich circumstellar medium. The progenitor paths for type IIn supernovae are unclear, at least one transient, SN2005gl has pre-explosion imaging revealing the progenitor to be a luminous blue variable. These luminous blue variables are massive evolved stars that undergo episodic mass loss which may form the required circumstellar material for the type IIn phenomenon. However recent studies on the environments of type IIn supernovae reveal that these transients are not strongly associated with regions of ongoing star formation.
These environmental studies are a powerful indirect method to constrain progenitor paths. In the first part of this thesis, I set out a classification scheme for type IIn supernovae and apply it to archival spectral data. Then using this sample with robust classifications, I observe the hosts of type IIn supernovae with the Liverpool Telescope, the Isaac Newton Telescope and the Las Cumbres Observatory Global Telescope Network 2m. Using these data, I create continuum subtracted Hα images and apply the novel pixel statistics technique, normalised cumulative ranking. This method is used to gauge the association of a SN position with the Hα emission in the host. There is a mass ladder in terms of this association, the more massive the progenitor, the better the supernovae follow the emission. I present the results of these pixel statistics as well as the radial distributions of type IIn supernovae in order to investigate possible progenitor routes.
In the second part of this thesis, I investigate the environments of classical novae in the Andromeda galaxy, M31. Classical novae are a subset of cataclysmic variable where a white dwarf accretes hydrogen-rich material from a companion via Roche-lobe overflow, Once sufficient material has been accreted, a thermonuclear runaway occurs on the surface of the white dwarf and a portion of the accreted material is ejected. Generally, classical novae can be split into two spectral classes, Fe II and He/N, based on their characteristic non-Balmer lines.
Previous work has suggested the existence of different populations of classical novae in terms of their radial distribution, or association to the bulge or disc of M31. I investigate the possibility that the spectral classes of classical novae can be separated based on their radial distributions. The progenitor systems of He/N classical novae may have a higher mass white dwarf and may be expected to be associate with the younger populations in the disc of M31. Firstly I present the largest spectroscopically confirmed M31 classical nova sample. Then as well as a radial analysis, for the first time, I will implement the normalised cumulative ranking method on classical novae. In this case with GALEX NUV and FUV. I compare the spectral classes to each other in terms of both their radial distributions and association to the UV emission.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	Supernovae; Classical Novae; Massive Stars; Observational Astronomy; Astronomical techniques; Transient environments
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
SWORD Depositor:	A Symplectic
Date Deposited:	01 Feb 2023 09:31
Last Modified:	01 Feb 2023 09:31
DOI or ID number:	10.24377/LJMU.t.00018770
Supervisors:	Habergham-Mawson, S, Darnley, M and James, P
URI:	https://researchonline.ljmu.ac.uk/id/eprint/18770

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