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Title: The progenitors of type Ia supernovae : what can we learn from the circumstellar medium around single degenerate systems?
Author: Booth, Richard Anthony
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2013
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While the progenitors of Type Ia supernovae (SNe Ia) have long been thought to be thermonuclear explosions of white dwarf stars, what triggers the explosion are still a topic of debate. This thesis considers constraints on single-degenerate progenitors of SNe Ia based on the presence of a Roche-lobe filling companion. The ejecta strips material from the companion, that maybe detectable via Hα emission during the nebular phase. Using the full structure from simulations produces line widths are larger than those produced in simple models. The structure formed by the ejecta-companion interaction produce a broken reverse shock that may be visible in X-rays via the Fe Kα line at the age of Tycho's supernova remnant (SNR). If the similar structures in Tycho’s SNR are produced this way then the companion star must have been massive, with M ~ 2 M. Detections of circumstellar material within the supernova provides another way to indirectly probe the companion star. Mass loss through winds or novae are expected to shape the circumsteller medium for single-degenerate progenitors and the velocities, v ~ 100 km s-1 appear to be consistent with recurrent nova shells, a model that is tested by analysing simulations of RS Ophiuchi. Models of RS Ophiuchi can explain the absorption lines seen around the 2006 outburst if the mass loss is 10−6 M yr-1,/sup>. The circumsteller medium is shown to produce in the velocity and relative strengths of the features seen in SN 2006X. However, whether density in the shells is high enough to produce the required recombination timescale and to overcome ionization by γ-rays for shells at 5 × 1016 cm remains uncertain.
Supervisor: Podsiadlowski, Philipp Sponsor: Engineering & Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Astrophysics (theoretical) ; astrophysics ; supernovae: type Ia ; stars: winds