ROSAT PSPC Observations of the Intermediate Polar TV Columbae

Abstract

The intermediate polar TV Columbae was observed for 8640s with the ROSAT PSPC. The best-fitting model to the 0.1-2.0 keV spectrum combines a power law with photon index α = 0.82 and a 54 eV blackbody, both observed through a column density of 4.6 x 10²⁰ cm^-2. No evidence is seen for line emission from the Fe L-shell complex. We observe an X-ray/optical flux ratio of 0.2: our measured X-ray photon flux is not sufficient to produce the He II λ1640 recombination line flux found by lUE. Some of the missing X-ray flux can be attributed to absorption in an accretion curtain. An additional very soft EUV component (e.g., a 20 eV blackbody) could provide sufficient photons in the 55-100 eV band to account for most of the He ii luminosity while remaining hidden to the PSPC and lUE. A second possibility is that the X-ray flux is indeed small and collisional excitation accounts for 80% of the He II λ1640 flux. Because of instrumental difficulties, we are unable to confirm the 32 minute period observed with EXOSAT and attributed to rotation of the white dwarf.