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Title: On dying stars : supernovae and their progenitors
Author: Fraser, Morgan
ISNI:       0000 0004 2741 7877
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2012
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In the last fifteen years, searches for the progenitors of core-collapse supernovae (SNe) in archival images have provided the crucial "missing link" between the final stages in the evolution of a massive star, and its explosion as a core-collapse SN. In this thesis, I present new detections and limits for core-collapse SN progenitors, together with a critical re-analysis of those already published. I present detailed studies of the progenitors of three nearby SNe. For the sub- luminous Type IIP SN 2009md, I find a coincident red supergiant progenitor with a mass of ~8 M in archival images, which is consistent with the low mass progenitors found for other faint Type IIP SNe. Such events appear to come from red supergiants at the lower extremum of the mass range for core-collapse. I discuss the intermediate Type IIP /L SN 2009kr, for which I find what appears to be a massive yellow supergiant progenitor. I consider possible explanations for the observed colour of the progenitor candidate at explosion, and the consequences for stellar evolution. I also analyse archival pre-explosion images of the site of the Type Ib SN 2009jf, for which a progenitor was not detected. I attempt to constrain the age of the stellar population in the locale of the SN, and use this to set a limit on the progenitor mass. I also extend the time- and volume-limited sample of core-collapse SNe presented by Smartt et al. (2009). I use this new data, together with an improved re-analysis of the original limits of Smartt et al., to set an upper limit on the mass of Type IIP and Type IIL SN progenitors of 20M, at a 95 per cent confidence level. This limit is lower than the most massive observed red supergiants, providing strong support for suggestions that some of the most massive red supergiants do not produce bright SNe, but rather collapse to form black holes either directly or via fall-back. Finally, I discuss some alternative approaches for understanding core-collapse SNe and their progenitors, including searching for progenitors in X-ray data, a survey for optically faint failed SNe, and a deeper search for a surviving companion to the progenitor of the Galactic SN Cas A.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available