Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709685
Title: Observations and modelling of super-luminous supernovae
Author: Nicholl, Matthew
ISNI:       0000 0004 6059 5042
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2016
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Abstract:
We present the results of extensive ground-based monitoring campaigns for a number of low- redshift hydrogen-poor (Type Ic) super-luminous supernovae (SLSNe). Our data make these some of the best-observed examples of this class. We use photometry and spectroscopy in the optical, UV and NIR to constrain their luminosities, velocities and temperatures. We measure the characteristic diffusion time for a large sample of published objects and use this to show that the ejected masses are typically larger than in normal-luminosity SNe Ic (including GRB-SNe). High ionisation may also be a factor in broadening their light curves. However, we show that even for the slowest-evolving objects, the time to reach peak brightness and inferred ejecta mass are well below the predictions for hypothetical pair-instability supernovae (PISNe). This is true even for slowly-fading SLSNe identical to the well-studied SN 2007bi - thought to be a strong candidate for a PISN. We argue that no SLSNe observed so far are PISNe. For one object caught soon after explosion, a double-peaked light curve seems to indicate an extended progenitor. These properties are studied using a semi-analytic light curve modelling code. Three possible power sources are investigated: radioactive 56Ni; a central engine such as magnetar spin-down; and interaction with a massive circumstellar medium. We find that the latter two can reproduce SLSN light curves, but 56Ni-powering requires unrealistic model parameters, even for slowly- fading objects. The observed spectra may help to break the degeneracy between central engine and interaction models. The lack of narrow emission or absorption lines, the presence of broad lines well before light curve maximum, high velocities with little sign of deceleration, the overall similarity to SNe Ic, and agreement with literature models for magnetar-energised ejecta all suggest that a millisecond magnetar (or possibly black hole accretion) engine is the most probable power source in SLSNe Ic.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.709685  DOI: Not available
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