Far Ultraviolet Observations of the Dwarf Novae SS Aur and RU Peg in Quiescence

Abstract

We have analyzed the Far Ultraviolet Spectrocopic Explorer (FUSE) spectra of two U Gem-Type dwarf novae, SS Aur and RU Peg, observed 28 days and 60 days (respectively) after their last outburst. In both systems the FUSE spectra (905 - 1182 A) reveal evidence of the underlying accreting white dwarf exposed in the far UV. Our grid of theoretical models yielded a best-fitting photosphere to the FUSE spectra with Teff=31,000K for SS Aur and Teff=49,000K for RU Peg. This work provides two more dwarf nova systems with known white dwarf temperatures above the period gap where few are known. The absence of CIII (1175 A) absorption in SS Aur and the elevation of N above solar suggests the possibility that SS Aur represents an additional accreting white dwarf where the surface C/N ratio derives from CNO processing. For RU Peg, the modeling uncertainties prevent any reliable conclusions about the surface abundances and rotational velocity.

arXiv commentAJ, Oct. 2004

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• A Far Ultraviolet Study of the Hot White Dwarf in the Dwarf Nova WW Ceti
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• A Far Ultraviolet Study of the Nova-like V794 Aquilae
• A Survey of Far Ultraviolet Spectroscopic Explorer Observations of Cataclysmic Variables
• Quantifying the Carbon Abundances in the Secondary Stars of SS Cygni, RU Pegasi, and GK Persei
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• FUSE Observations of the Dwarf Novae UU Aql, BV Cen, and CH UMa in Quiescence
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