Spectrum synthesis of accretion disks in partial eclipse

We have modified a spectrum synthesis code for accretion disks in binary st ar systems, to deal with the case of a disk that is partially eclipsed by t he mass-losing star. The known Roche geometry of the binary system permits the correspondence to be made between the spectrum observed over some phase interval and the regions of the disk that contribute to the spectrum. The code can generate simulated observations corresponding to arbitrary phase i ntervals, with arbitrary spectral sampling and resolution. This capability clearly includes generating broadband light curves as a limiting case. The use of angle-dependent specific intensities means that limb-darkening effec ts are automatically taken into account. We present trailed-spectrogram and other representations of the partially e clipsed disk spectra of representative models of cataclysmic variables. The spectra are shown versus orbital phase, for portions of the ultraviolet sp ectral region accessible to the Hubble Space Telescope. We illustrate the b ehavior of blended features through eclipse and comment on the sensitivity of the synthesized spectra to the parameters of the input model, such as th e stellar masses, mass transfer rate, and orbital inclination. Compared wit h out-of-eclipse spectra of the entire disk, observations during eclipse sh ould have the advantage for diagnostic purposes of showing (1) deeper indiv idual lines, (2) reduced blending of lines, and (3) an effectively smaller range of effective temperatures contributing to the observed spectrum. Thes e advantages are especially important in analysis of the ultraviolet spectr a of disks.