OPTICAL SPECTROSCOPY OF Z-CANIS MAJORIS, V1057-CYGNI, AND FU ORIONIS - ACCRETION DISKS AND SIGNATURES OF DISK WINDS

We obtained high-resolution, high signal-to-noise ratio, 3985-4920 angstrom, 4940-6830 angstrom, and 8030-9510 angstrom spectra of V1057 Cyg, Z CMa, and FU Ori at the Mayall telescope at KPNO to examine predictions of the accretion disk model of Kenyon, Hartmann, & Hewett. Synthetic disk spectra are calculated assuming the temperature gradient, T(R), of a classical accretion disk, and assuming that disk photospheres can be modeled by adding contributions from concentric disk annuli represented by spectra of supergiant stars having T(eff) almost-equal-to T(R). We examine variation of absorption line width with wavelength for synthetic and FUor spectra, and find good correlations for the model and two FUors (V1057 Cyg and Z CMa). We also investigate variation of line width with lower excitation potential and find a subtle effect, less useful as,a disk diagnostic. We subtract synthetic spectra from object spectra to investigate overall goodness of fit. Given the simplicity of the model, we find remarkably good fits for all three objects for wavelengths longer than approximately 5000 angstrom. The mismatch at all wavelengths is due to nondisk components to the FUor spectra. We examine these residual features in V1057 Cyg and Z CMa. Most of the strongest features are either emission or P Cygni lines, suggesting origin in powerful winds driven by these objects. For FU Ori, most residuals are absorption features, as expected if FU Ori has lower surface gravity than do supergiants, or if wind absorption is particularly strong.