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Session 79 - CVs and Novae.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center

[79.05] Accretion Disk Models for VOYAGER, HUT, and FUSE Far--UV Spectra

R. A. Wade (Penn State U.), I. Hubeny (NASA/GSFC)

Several past and future space missions have the capability to observe spectra of cataclysmic variables in the far--UV spectral region (from just short of the Lyman limit to longward of Lyman-\alpha). These include the VOYAGER Far--UV Spectrometers (FUVS), the Hopkins Ultraviolet Telescope (HUT; flew on ASTRO--1 and ASTRO--2), and the planned FUSE mission. We present a model spectrum grid for axi\-symmetric, steady--state accretion disks in cataclysmic variable systems, where the accreting object is a white dwarf. The white dwarf mass and radius are varied on the grid, 0.35 \leq M_wd/M_ødot \leq 1.21 and 1.14 \geq R_wd/(10^9 cm) \geq 0.38 respectively. The mass accretion rate is also varied, on the range -10.5 \leq \log dM/dt \leq -8 (M_ødot yr^-1). A standard Reynolds number description of the viscous dissipation is adopted. The local plane--parallel approximation is used, LTE is assumed, and irradiation of the disk or communication between different radial zones of the disk is ignored. Within these assumptions the vertical structure is calculated in a self--consistent manner to ensure both hydrostatic equilibrium and energy balance, using a restricted set of opacities. Ring and full--disk spectra are constructed from these models using a full line list, taking into account self--consistent limb darkening and Doppler shifts due to Keplerian orbital motion of the gas.

The spectral region from 850 Å\ to 1350 Å\ is covered, and spectra at several inclinations are tabulated. The spectra will be made available electronically with a sampling interval and resolution sufficient to allow the study of FUVS and HUT spectra, and can be resampled for FUSE and other missions. The models serve as a benchmark against which more complicated models, perhaps including winds, can be compared. Representative spectra and some interesting trends are shown.

Supported by NASA grants NAG5--2125 and NAGW--3171.

Program listing for Wednesday