Mullard Space Science Laboratory

R. E. Cole
Soft X-ray emission from possible white dwarf candidates

1986 (supervisor A. M. Cruise)

This thesis presents data taken with the soft X-ray experiment on the Ariel 6 satellite launched in 1979. The experiment was jointly built by the Mullard Space Science Laboratory, University College London and the University of Birmingham. Data were aquired on a number of objects which might contain a white dwarf star. These are small, dense stars near the end of their life.

In chapter 1 a review of the ways in which such a star could emit X-rays is given. In chapter 2 a description of the experiment is presented along with the methods of instrument operation and data analysis used.

Chapter 3 goes on to describe HZ43, a white dwarf which emits X-rays just through having a high surface temperature. The white dwarf in the AN UMa system (chapter 4), however, has a strong magnetic field and material from the companion star is channelled down the field lines onto the poles of the white dwarf from where the X-rays come. Chapter 5 describes a model developed for the accretion flow onto the white dwarf in AM UMa.

Cygnus X-2 (chapter 6) is a well-studied source where it is not known if the compact object is a white dwarf or the more compact neutron star. Soft X-ray data can shed light on this problem.

Chapter 7 discusses work carried out on the Wide Field Camera which will carry out a survey of the whole sky at extreme UV and very soft X-ray energies when it is launched on the Rosat satellite. The last chapter describes ray tracing work on the Ariel 6 instrument, software written to aid in-orbit operations and modelling of solar radiation scattering.


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