Mullard Space Science Laboratory

C. H. James
X-ray Studies of Intermediate Polar PQ Gem
2001 (supervisor: G. Branduardi-Raymont)

This thesis concerns an X-ray study of the intermediate polar (IP) magnetic cataclysmic variable (MCV) PQ Gem, which exhibits variable circular polarisation (indicative of a relatively high magnetic field) and a secure soft X-ray spectral component. These are unusual properties for an IP MCV. The scope of the thesis includes V405 Aur and RX J1712.6-2414, IPs which exhibit some of PQ Gem's unusual characteristics. This enables preliminary assessment of the generality of the PQ Gem's results.

The first three chapters are devoted to the introduction of the main characteristics and processes taking place in IPs, relevant previous findings about the three IPs under investigation and a description of the data, its reduction and analysis techniques employed. The focus of the analysis (Chapter 4) is to determine the role played by absorption and the changing visibility of the emission region(s) in forging the observed modulation of the light curves of PQ Gem over the spin period. It is concluded that both play a part. The phased-resolved spectroscopy shows a strong correspondence between the variation of the covering fraction of a partial absorber component and the hardness ratio. Possible accretion scenarios are examined and a modification of the accretion curtain model (Rosen et al. 1988) proposed. The mass of the white dwarf is also calculated. The analyses of V405 Aur and RX J1712.6-2414 (Chapters 5 & 6) resemble those of PQ Gem. The results are interpreted both in their own right and compared to those of PQ Gem. An explanation for the varying prominence of the double pulse in the spin folded light curves of V405 Aur is suggested.

The final chapter pulls together the results from the preceding chapters and makes a preliminary assessment as to the applicability of the findings on PQ Gem to the IP subclass of MCVs as a whole.


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