The properties of the SC stars and chemical composition of UY centauri

Doctoral Thesis


Permanent link to this Item
Journal Title
Link to Journal
Journal ISSN
Volume Title

University of Cape Town

This is primarily an observational thesis concerned firstly, with improving our knowlegde of the 12 SC stars, defined as a group by Catchpole and Feast (1971) and secondly, with determining the chemical composition of UY Cen, the brightest member of the group. An atlas, based on 13 A mm-1 spectra is presented for the S star π Gru and the C star 19 Psc between 5430 and 6850 A. In order to overcome the problems caused by the high density of absorption lines, we use a method of line identification that relies on the statistical interpretation of intensity against wavelength-agreement and Intensity against Excitation diagrams. The objective being to determine which elements are present in the spectrum before assigning identifications to individual lines. The spectrum is found to be rich in 's' process elements and shows weak molecules of both carbides, oxides and hydrides. U to L (0.36 to 3.4μ) photometry is listed for all the stars and shows them to be a very homogeneous group. A set of wavelengths derived from the line list is used to find the radial velocities of all the stars. A solar model atmosphere, with pure absorption as the method of line formation, is used to derive astrophysical log gf values from solar equivalent widths and meteor abundances. The model atmosphere also shows, that for our set of CN equivalent widths, both the CN abundance and the derived isotope ratio depend on the adopted C/O ratio.

Bibliography: p. 185-292.