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Modelling heteroscedasticity in variable star periods

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dc.contributor.advisor Prof. F. Lombard; Dr. M.C. Koen en_US
dc.contributor.author Human, Johannes Urbanus
dc.date.accessioned 2012-01-24T05:41:52Z
dc.date.available 2012-01-24T05:41:52Z
dc.date.issued 2012-01-24
dc.date.submitted 2004
dc.identifier.uri http://hdl.handle.net/10210/4281
dc.description M.Sc. en_US
dc.description.abstract A concern for astronomers is to determine whether the period of a variable star stays constant over time. One aspect that has been neglected in the past when testing for constant period is that the variance of the observed period decreases over time, at least for some stars. In this short dissertation, two models that account for the change in variance will be investigated. One model assumes an exponentially decreasing variance while the other allows for an abrupt change in the variance. For each of these two models a test for a change in variance is proposed. The properties of the estimates in the time and frequency domain are discussed and we show that for these models, estimation in the frequency domain fails. The models also provide for the presence of a non-constant period. The possibly changing period is modeled by a sum of low-frequency cosine terms. The number of cosine terms is determined using an order selection test introduced by Aerts, Claeskens and Hart (1999). We show that not accounting properly for a changing variance may result in a changing period not being detected. en_US
dc.language.iso en en_US
dc.subject Heteroscedasticity en_US
dc.subject Analysis of variance en_US
dc.subject Astronomical photometry en_US
dc.title Modelling heteroscedasticity in variable star periods en_US
dc.type Mini-Dissertation en_US

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