Final PhD Oral Examination (Thesis Title: “White Dwarf Populations in Globular Clusters”)

Speaker: 
RYAN GOLDSBURY
Event Date and Time: 
Tue, 2016-03-08 12:30 - 14:30
Location: 
Room 203, Graduate Student Centre
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 
Public

ABSTRACT:
The thesis details three distinct projects that explore stellar populations in Milky Way globular clusters. In the first, a method of modelling mass segregation in clusters is presented. The model is fit to 54 clusters and the best fit parameters are presented in tabular form. The newly derived parameter that indicates the amount of mass segregation correlates strongly with other dynamical cluster parameters. In the second study, white dwarf data in the cluster 47 Tucanae are used to construct an empirical relation between temperature and time for these stars. The modified data are compared to theoretical cooling models from four different research groups. We find disagreement between all of the models and the data. The models are also inconsistent with each other. In the third investigation, new UV white dwarf data in 47 Tuc are used to constrain the hydrogen mass fraction and neutrino production rates in cooling white dwarfs. A much different approach from the second project is used. The data are left untouched and the model is transformed into the space in which the data exist. Using the unbinned maximum likelihood statistic, the model's parameter space is explored with MCMC sampling. A constraint on the rate of neutrino production in white dwarfs comes from this analysis.

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