Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000pasp..112.1611u&link_type=abstract
The Publications of the Astronomical Society of the Pacific, Volume 112, Issue 778, pp. 1611-1616.
Astronomy and Astrophysics
Astronomy
11
Accretion, Accretion Disks, Stars: Novae, Cataclysmic Variables, Stars: Individual (Cn Orionis), Stars: White Dwarfs
Scientific paper
We have carried out a synthetic spectral analysis of five IUE NEWSIPS archival spectra of the peculiar, very active dwarf nova CN Orionis taken at the system's lowest flux levels during quiescence. AAVSO data indicate the visual magnitude V~14 for CN Ori at this time. On the assumption that the white dwarf contributes significantly to the far-UV light of the system, we have computed a two-parameter grid of synthetic, high-gravity spectra in LTE with solar composition using TLUSTY195 and SYNSPEC42 and carried out fits of these pure photospheric models to the far-UV continuum and narrow absorption line spectra. We find that the far-UV spectrum in quiescence is well represented by a hot (Teff=30,000 K, logg=7) white dwarf with probable subsolar silicon abundance and all other observed metal transitions at essentially their solar values. For comparison, we have fitted optically thick accretion disk models to the same spectra for Mwd=0.80 Msolar and disk inclination angle i=60deg for accretion rates M=10-10.5 and 10-9.5 Msolar yr-1. We compare the Teff of CN Ori, one of a handful of dwarf novae above the period gap with a model photospheric analysis, to all other dwarf novae with white dwarfs of known Teff derived using white dwarf model atmospheres. We find evidence that the white dwarfs in dwarf novae above the period gap are hotter than the ones below the gap. This trend suggests more heated, younger degenerates above the gap and is consistent with the overall empirical evidence that mass transfer rates in dwarf novae above the period gap are higher than mass transfer rates in systems below the gap.
DiTuro P.
Lyons Kelly
Mittal Rajat
Nadalin Ira
Sion Edward
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