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An automated method of determining the relative line separations on digitized blended stellar spectra has been developed. A pair of standard profiles are fitted to the observed blended profile by allowing the standards to relax in position and amplitude until a least-square 'best fit' is obtained. The technique has been tested on numerous blends of known separation and it has been shown that with certain restrictions on the relative amplitudes it is not susceptible to systematic errors. Blended hydrogen and helium lines in two B-stars have been separated to < 100 km/sec at 30 A/mm with a probable error of 15 km/sec. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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A sample of K stars has been taken from several objective-prism plates. This sample will be studied photometrically to answer two basic questions. First, is it feasible to subclassify these stars as K1, K2, K3, ... etc., which reflect temperature differences? This has been done by determining color indices of the stars in the sample and taking an average color index for stars in each subclass. Standard deviations were used to ascertain if differences between the means are statistically significant. Second, are there any red giant stars in our sample? If so, is giant contamination related to temperature classification? The B-V and V-I color indices for the program stars were compared to those of known dwarf and giant stars in a two-color diagram. The results of this study will permit more informed decisions about the value of spectral classes for K stars. Also distances (photometric parallaxes) were computed from the photometric data obtained. / Department of Physics and Astronomy

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Spectroscopic observations of 18 of the brighter Be and 0e stars in the Northern Hemisphere have been presented in this project. About 900 spectrograms were secured and measured using the more objective numerical technique (REDUCE and VCROSS) to obtain as many accurate radial velocities as possible for these stars. The analysis of these measurements has demonstrated clearly, that most of these early-type stars are indeed variable in radial velocity, while a real periodicity in the radial velocities of some of the programme stars is found. The long-term periodicities were attributed to the binary nature, while the short ones could be ascribed to the pulsation phenomenon. Orbital elements are determined for four newly discovered binary systems, and improved orbits are determined for four known binaries. Five other stars display short time-scale periodicity (less than 1.5 days) attributable to radial or non-radial pulsation, whilst three variables show little evidence for periodicity. Only two stars are found to have constant radial velocities. A brief summary of the properties of Be stars and all the available models to explain the Be phenomenon is presented in chapter one. Chapter two contains a brief description of the observing equipment and the techniques used. The reasons for selecting the programme stars are given in the same chapter. A complete explanation of the measuring technique used in this investigation is given in chapter three. In chapter four, all the analyses and the results for each star are given individually, while a discussion of previous work on these stars appears in the relevant sections. The final chapter contains a discussion of the results from this study together with an analysis of the energy distributions of the programme stars, compiled by the author from published fluxes and photometry from the ultraviolet to the infra-red parts of the electromagnetic spectrum. Some consideration of future work to be done on these types of stars is also given.