Time-series photometry of rapidly pulsating stars and a transiting extrasolar planet

Abstract

This thesis describes a programme of research that employed the techniques of high-speed photometry to make astronomical observations. This observational procedure is required in order to successfully monitor brightness changes that occur over relatively short time scales, which for some of the stars discussed in this thesis, involves intervals as short as ~ 100 seconds. All of the observations described here were obtained using a three channel photometer that enabelled the brightness record of an astronomical object to be monitored with a time resolution of a few seconds (typically 10) over continuous periods ranging up to more than 10 hours, and limited only by the length of the night. Chapter 1 provides a very brief introduction to pulsating stars in general and a simple version of the underlying theory. It then looks in more detail at pulsating white dwarfs stars, which were the target objects for most of the observational work presented in this thesis. Chapter 2 describes the workings of the VUW three channel photometer, used to acquire the observational data described in the thesis, and it also gives an overview of the techniques of time-series photometry. In particular, it summarises the data reduction techniques employed to extract the quantities of interest from the data. A mainly pictorial summary of example data sets for all the stars observed (a "whanau of pulsators") as part of the thesis programme is provided in Chapter 3. Much of the observational work referred to here was part of a more extensive exercise than this thesis (eg Whole Earth Telescope campaigns), so references are provided to a number of papers in which the the writer has been included as a co-author. Detailed conclusions of the joint work can be obtained in these references and only brief relevant commentary, largely obtained from the standalone data sets, is given here. The chapter concludes by discussing discrete Fourier transforms of the reduced light curves for two of the white dwarf pulsators so illustrating how Fourier techniques are used to detect frequencies in the light curves. Chapter 4 forms a core part of the thesis. It features both observational material obtained by the author and independent analysis of the transit light curves for the first extrasolar planet detected this way. At the time (1999) it was unique, and it extended our then knowledge of this still very special extrasolar planet. Finally there are 4 appendices. Appendix A lists the publications the writer has been included in as a co-author as a direct result of the mainly observational work reported in this thesis. Appendix B gives some details of the programs used as part of the analysis work in the thesis. Appendix C describes in some detail the plane parallel atmosphere model for absorption and scattering effects for star light traversing the Earth's atmosphere to reach an observer on the ground. This model was used to extract the best Chapter 4 transit light curves from the observations. And, Appendix D presents a brief description of the conditions faced by an astronomer when observing from an open dome at an elevation of 4200 metres in winter time in Hawaii. The author experienced 5 weeks in total of these observing conditions at Mauna Kea Observatory, so can without fear of contradiction refer to himself as an experienced veteran.