J. P. Osborne
The Soft X-ray Telescopes on Ariel 6 and EXOSAT Observations of Cataclysmic Variables
1989 (Supervisor: J. L. Culhane)

There are two major sections to this thesis, chapters 2, 3 and 4 describe the MSSL/Birmingham soft X-ray telescopes on the Ariel 6 satellite, chapters 5, 6, 7 and 8 describe the European X-ray satellite EXOSAT and discuss observations of magnetic cataclysmic variables made with it.

The first chapter is an introduction. It contains descriptions of X-ray emission and absorption processes, cataclysmic variables and proportional counter operation.

The MSSL/Birmingham soft X-ray telescopes are described in chapter 2. They were low background, non-imaging detectors sensitive to 0.1 - 2.0 keV X-rays. The energy calibration of the telescope proportional counters is then discussed. Chapter 4 briefly deals with the in-flight operation of Ariel 6 and the soft X-ray telescopes, and reviews some results.

Chapter 5 introduces EXOSAT, its low energy imaging telescopes (0.05 - 2.5 keV), medium energy proportional counter array (1 - 10 keV), gas scintillation proportional counter (2 - 30 keV), and the on-board computer and data packaging are described. An in-flight calibration of the star tracker - low energy telescope misalignment is given.

Chapter 6 describes a 1983 EXOSAT observation of the AM Herculis binary E2003+225. The soft X-ray light curve was found to be complex. A measurement of the soft X-ray temperature using the grating was made. Estimates of the luminosities of the accretion powered spectral components are compared. The next chapter describes the 1985 EXOSAT observations of E2003+225 in which a new form of soft X-ray light curve was discovered.

The discovery of a new AM Her binary, EXO 033319-2554.2, is described in chapter 8. Eclipses in the soft X-ray light curve are due to the secondary star and constrain the geometry of this system. The soft X-ray luminosity exceeds the radiative lumniosity of the shocked accretion stream, contradicting standard theory.