Synthetic Spectrum Constraints on a Model of the Cataclysmic Variable QU Carinae

Abstract

Neither standard model SEDs nor truncated standard model SEDs fit observed spectra of QU Carinae with acceptable accuracy over the range 900-3000 Å. Nonstandard model SEDs fit the observation set accurately. The nonstandard accretion disk models have a hot region extending from the white dwarf to R = 1.36R_WD, a narrow intermediate-temperature annulus, and an isothermal remainder to the tidal cutoff boundary. The models include a range of \dot{M} values between 1.0 × 10^-7 and 1.0 × 10^-6 M_⊙ yr^-1 and limiting values of M_WD between 0.6 and 1.2 M_⊙. A solution with M_WD = 1.2 M_⊙ is consistent with an empirical mass-period relation. The set of models agree on a limited range of possible isothermal region T_eff values between 14,000 and 18,000 K. The model-to-model residuals are so similar that it is not possible to choose a best model. The Hipparcos distance, 610 pc, is representative of the model results. The orbital inclination is between 40° and 60°.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555, and the NASA-CNES-CSA Far Ultraviolet Explorer, which is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.