A photometric and spectroscopic study of selected southern, chromospherically active stars.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The results of a combined photometric and high-resolution spectroscopic study of southern active-chromosphere stars selected from the ROSAT Bright Source Catalogue are presented. The star CS Ceti (HD 6628) is shown to be a single-lined spectroscopic binary and an orbital solution derived from radial-velocity measurements is presented. Evidence that one of the stars is an F-type dwarf and the other a highly active G-type subgiant is presented, together with information on the apparently asynchronous rotation of the latter and the spatial origin of its Hα emission. The system BB Sculptoris (HD 9770) is shown to include a chromo spherically active eclipsing binary of the BY Dra class and evidence that this is the star previously known as HD 9770B is presented. A precise orbital period is presented. Further evidence is presented to show that the star known as HD 9770A is also a binary system, one member of which dominates the absorption spectrum of BB Scl. Two further stars selected from the Bright Source Catalogue are recommended for further study: HD 147633 in which a known binary system is found to contain a further chromospherically active, short-period, double-lined spectroscopic binary; and HD 222259, a known chromospherically active binary in the light curve of which a spot wave which persists on a time scale of years has been found and for which a precise period is presented. In addition, the results of a continuing program of observation of the chromospherically active system GT Muscae (HR4492) are presented. Evidence is presented that the known eclipsing binary system HD 101380 consists of A0 V and A0/2 V stars, and the period of the system is further refined. A combined photometric and high-resolution spectroscopic study of the active binary HD 101379 provides evidence that its active star is a late G-type bright giant rather than a K4 star as suggested in a previous study. Evidence that the source of its Ha emission lies in the space between the stars is discussed. High-resolution spectra of two chromospherically active stars - CF Tucanae (HD 5303) and HD 219025 - observed for other programs are also presented and briefly discussed.