Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21541625m&link_type=abstract
American Astronomical Society, AAS Meeting #215, #416.25; Bulletin of the American Astronomical Society, Vol. 42, p.270
Astronomy and Astrophysics
Astronomy
Scientific paper
We have carried out a combined Hubble Space Telescope and FUSE FUV spectroscopic analysis of the prototype dwarf nova SS Cygni during quiescence. The FUSE and HST spectra were obtained at comparable times after outburst and have matching flux levels where the two spectra overlap. In our synthetic spectral analysis, we have used SS Cygni's accurate HST FGS parallax giving d = 166 pc, a newly determined mass for the accreting white dwarf (Bitner, Robinson, & Behr, 2007, ApJ) of Mwd = 0.81 Msun (lower than the previous, widely used 1.2 Msun) and a widely adopted reddening of E(B-V) = 0.04. Our best-fit model solution to the combined HST + FUSE spectral energy distribution consists of a hot white dwarf with Teff = 45,000K, log g = 8.3 with a solar composition accreted atmosphere. Accretion disk models matching a distance of 166 pc fit badly in the FUSE range while, if the distance is a free parameter, the only accretion disk model which fits well is for a distance of 600-800 pc and the accretion rate (10-8 Msun/yr!) is unacceptably high for a dwarf nova in quiescence. We discuss the implications of the white dwarf temperature for the time-averaged accretion rate and long term compressional heating models.
This work is supported by NSF grant AST08-07892 and NASA ADP grant NNX08AJ39G, both to Villanova University, the Villanova Undergraduate Research Award and partial support from the Delaware Space Grant Consortium.
Godon Patrice
Myszka Janine
Sion Edward
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