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K.J. Kolb, J.K. Miller, E.M. Sion (Villanova Univ.)
We present the results of an ultraviolet spectroscopic study of the hot components in the S-Type symbiotic variables EG And and SY Mus. Our study utilized orbital-phase resolved IUE archival low resolution and HST archival spectra, including all available images obtained at superior spectroscopic conjunction (when the accreting hot white dwarf is in front of the red giant). While these systems are among a handful of symbiotic variables in which the photospheric continuum from the hot white dwarf is thought to be the dominant source of light in the far ultraviolet, the dominant presence of an accretion disk cannot be ruled out. To deepen our insight on the hot components, we have carried out the first LTE and NLTE model atmosphere and model accretion disk synthetic spectral fits to the far UV continuum using the codes TLUSTY198, SYNSPEC45 and TLUSDISK. We found that the best model fits, consistent with the Hipparcos parallax of EG And and the distance estimates of SY Mus, were provided by model accretion disks. The best accretion disk fits to EG And and SY Mus had accretion rates 10-8 Msun/yr and disk inclination angles of 60 to 75 degrees. We also present a comparison between the LTE and non-LTE fits, the effects of iron-peak absorbing curtains and the results of composite white dwarf plus accretion disk fits.
This work was supported by NSF grant AST99-01955 to Villanova University and by summer undergraduate research support from the NASA-Delaware Space Grant Consortium.
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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.