Abstract
We have analyzed Hubble Space Telescope (HST) archival and IUE NEWSIPS archival SWP spectra of the dwarf novae CM Del and AH Her obtained when AAVSO light-curve data indicated the occurrence of dwarf nova quiescence. We have computed synthetic, high-gravity spectra in LTE with solar composition using TLUSTY195 and SYNSPEC42 and have carried out fits of these models to the far-UV continuum and narrow absorption line spectra. For CM Del, we find that the far-UV spectrum is dominated by a hot (Teff = 22,000 K and log g = 8) white dwarf, but reliable information on the metal abundances is unavailable because of the quality of the data. For AH Her, we find evidence for a hot white dwarf with Teff = 27,000 K and log g = 8, with subsolar abundance for Si. An HST spectrum (GHRS G160M) of AH Her reveals blue-asymmetric Si IV profiles. If this is due to wind outflow, we derive a single-scattering, upper limit, mass-loss rate of 10-9 M⊙ yr-1. Synthetic profile fits to 12 co-added HST medium-resolution G160M spectra of the Si IV (1393, 1402 A) resonance doublet of CM Del yield a white dwarf rotational velocity estimate of v sin i = 400 km s-1 and Si/H = 1 times solar. The value of v sin i for CM Del is discussed in the context of angular momentum transfer and rotation rates for other cataclysmic variable, primary degenerate stars.
Published Version
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