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Title: Observational constraints on the progenitors of Type Ia Supernovae
Author: Dimitriadis, Georgios
ISNI:       0000 0004 7225 2389
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2017
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This thesis investigates observational signatures and provides constraints on the progenitors of Type Ia Supernovae (SNe Ia), one of the most powerful cosmological probes, with a profound impact on understanding the evolution of the universe. By exploiting rich observational datasets, from powerful transient surveys, and extensively analysing them, we provide an insight into the long-standing progenitor problem. At first, we investigate the late-time evolution of the SN Ia light curve. Using the Palomar Transient Factory (PTF) observations of SN2011fe, added with external literature data, we achieve an unprecedented photometric coverage of the late-time light curve of a SN Ia, spanning from 200 to 1600 days after maximum, with remarkable temporal density. A combination of photometry and spectroscopy at these phases allows us to construct a pseudo-bolometric light curve and physical models that describe the behaviour of it are considered. Our main results are the explanation of the bolometric light curve by radioactive inputs of the 56Ni and 57Ni decay chains, with the estimated amount of 57Ni to be relatively large, indicating a high central density explosion environment. Moreover, our pseudo-bolometric light curve is not consistent with models that have complete trapping of the produced charged leptons, with models that allow for positron/electron escape or an infrared catastrophe (IRC) adequately describing the evolution. Finally, we studied a sample of 49 PTF SN Ia with late-time photometric coverage, finding no significant deviation on their light curve evolution compared to SN2011fe, and provide an upper limit on the hydrogen rich material at the site of the explosion to be ≤0.87 M". For the last part, we turn our focus to the spectroscopic class of 91T-like overluminous SNe Ia, by studying two members of this class: SN2014eg and SN2016hvl, for which we present their rich data set and provide physical parameters that describe them. Our results show that the highly reddened SN2014eg is a slightly less luminous 91T-like, with a 56Ni mass of 0.573 M", with indications of circumstellar material (CSM) at the site of the explosion, while SN2016hvl is a 91T-like with 0.767 M" mass of 56Ni. Finally, we study the host galaxies of the PTF 91T-like SNe Ia, and we find that they preferentially explode in active galaxies, with moderate to high star formation rates and a range in their stellar masses.
Supervisor: Sullivan, Mark Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available