The Iron Curtain Effect in the Ultraviolet Spectra of Dwarf Novae Z Cha and OY Car

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Session 46 -- Novae
Display presentation, Wednesday, 1, 1994, 9:20-6:30

[46.05] The Iron Curtain Effect in the Ultraviolet Spectra of Dwarf Novae Z Cha and OY Car

R.A.Wade (Penn State U.), F.H.Cheng (STScI/U.Md.), I. Hubeny (GSFC/USRA)

We model the ultraviolet spectra of the quiescent dwarf novae Z Cha and OY Car, obtained in 1986 with the SWP camera of the {\it International Ultraviolet Explorer}, on the assumption that the flux is due to the central white dwarf seen through a haze of absorbing material. This material is optically thin in the continuum but thick in the lines of many atomic species, chiefly of iron-peak elements. These IUE\/ observations are long exposures covering several orbits, and so they do not unambiguously refer to the white dwarf alone. This differs from the 1991 observation of OY Car's white dwarf by the Faint Object Spectrograph on HST , which was made using time-tagged eclipse spectrophotometry as discussed in Horne et al. ~(1994). The HST\/ data also have the advantage of a photon counting detector. Nevertheless, there is interest in using the {\it IUE\/} data to observe the so-called ``Iron Curtain'' of OY Car at a different epoch, and to extend the study of the Iron Curtain to another dwarf nova in quiescence, Z Cha.

Results in terms of multiple-parameter fits for the white dwarf temperature and solid angle, and the column density, temperature, number density, and turbulent broadening of the Iron Curtain of each star, are discussed. An attempt is made to be consistent with the optical photometry of the white dwarfs, as determined by Wood et al. (1986, 1989).

Supported by NASA grant NAG 5-703 and NASA/STScI grant GO-2380.

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