ROSAT and HST observations of magnetic cataclysmic variables.
thesisposted on 19.11.2015, 09:18 authored by Kathryn L. Clayton
This thesis describes principally ROSAT and HST observations of magnetic (or proposed magnetic) cataclysmic variables. Chapter 2 details a ROSAT observation of the polar EK UMa. The orbital light curve reveals a single bright phase. During this bright phase deep dips in the flux are seen, consistent with accretion stream occultation. The soft X-ray spectrum has an unusually high temperature of 50 KTBB 62 eV. No hard X-ray flux is detected. Chapter 3 details ROSAT observations of proposed intermediate polars SW UMa and 1H0709-360. The previously reported X-ray/optical periodicities in SW UMa were not detected. Spectral analysis indicates a two-temperature model is appropriate. The weak signal from 1H0709-360 precludes a detailed spectral analysis. 1H0709-360 has dropped in flux by ~ 2 orders of magnitude since its detection. The intermediate polar classification of these two systems remains unconfirmed. Chapter 4 describes ROSAT and contemporaneous optical and HST observations of the intermediate polar AE Aqr. During this observation X-ray flares were detected for the first time. The white dwarf spin modulated count rate increased only slightly with increased intensity. AE Aqr has an unusually soft spectrum which is only fit by a two temperature optically thin plasma emission model. Chapters 5 and 6 detail ROSAT, HST, EUVE and complementary optical observations of the polar QS Tel. The soft X-ray/EUV data showed a bright-faint morphology. The EUVE observations, ~ 1 year later, revealed a change in morphology, indicating that both poles were active. A deep narrow dip is observed in both the ROSAT and EUVE observations. The HST (FOS) observation had a mean spectrum of an underlying continuum with strong emission lines superposed. Orbital modulation was present in both. A narrow dip is observed in the continuum fold which is consistent with the dip observed by ROSAT and EUVE.