2005ApJ...623..425H

We have obtained FUSE (905-1187 Å) spectra of the nonmagnetic cataclysmic variable Z Cam during a period of quiescence. The spectrum resembles that of a hot (57,000 K) metal-enriched white dwarf. A high effective temperature is consistent with the expectation that dwarf nova systems that show standstills, as Z Cam does, have higher than normal time-averaged mass accretion rates. It is also consistent with current estimates for the mass and distance to Z Cam. A white dwarf model in which 29% of the surface has a temperature of 72,000 K and the rest of the surface is at 26,000 K also reproduces the spectral shape and the continuum flux level at the nominal distance and white dwarf mass, and is a somewhat better statistical fit to the data. A second component could be due to a rotating accretion belt, a remnant of an outburst that ended 11 days prior to the FUSE observation, or ongoing accretion. We favor the uniform-temperature model for Z Cam, largely because the data do not require anything more complicated. We have compared the quiescent spectrum with an archival spectrum of Z Cam in standstill, obtained with ORFEUS. The standstill spectrum is described well by a disk accreting at M{dot}_disk=7⁺⁴_–2x10¹⁶g/s, where the errors depend on the assumed inclination. The quiescent spectra cover a full orbital period and are time-resolved to ∼500 s. No variability was observed in the continuum during the observation, but the depth of many of the absorption lines increased between orbital phases 0.65 and 0.81. We attribute this effect to absorption by material associated with the accretion stream, which is easier to understand if the inclination is near the maximum allowed value of 68°.