AAS 204th Meeting, June 2004
Session 63 Exploding Stars
Poster, Wednesday, June 2, 2004, 10:00am-7:00pm, Ballroom

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[63.05] A Disk and Photosphere Model Analysis of the Dwarf Nova YZ Cancri in Outburst and Quiescence

R. Percy, E.G. Barron, E.M. Sion (Villanova University)

We have analyzed IUE Archival Spectra of the SU UMa type dwarf nova YZ Cancri in both outburst and quiescence using high gravity photosphere models and optically thick accretion disk models. In our analysis, we use the newly determined parallax for YZ Cancri by Thorstensen (2003, AJ, 126, 3017) and Harrison et al. (2004, AJ, 127, 460). Through composite white dwarf plus accretion disk models, our best-fit for outburst yields an accretion rate of 2.5 \times 10-9Msun/yr, a white dwarf mass of 0.8Msun, and a disk inclination angle of 41deg with the accretion disk accounting for nearly 100% of the FUV flux. This value is higher than that found b Patterson (1984, ApJS, 54, 443). Longward of 1620Å, the observed spectrum departs from the predicted energy distribution of a steady state disk. Our analysis of the IUE spectrum in quiescence with a composite disk plus photosphere model yields a best-fit for a white dwarf temperature of 23,000K, mass of 0.8Msun, and an accretion rate of 1 \times 10-10Msun/yr for a disk inclination angle of 41deg. The scale factor of this fit provides a distance in excellent agreement with the parallax distance of 260pc. The white dwarf contributes 24% of the FUV flux while the accretion disk contributes the remaining 76%. The implications of these results will be discussed. \newline \newline We acknowledge support for this research from NSF Grant AST99-09155, NASA ADP Grant NAG5-11182, and by the Delaware Space Grant Consortium (EGB).

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