Hubble COS Spectroscopy of the Dwarf Nova CW Mon: The White Dwarf in Quiescence?

Abstract

We present a synthetic spectral analysis of the HST COS spectrum of the U Geminorum-type dwarf nova CW Mon, taken during quiescence as part of our COS survey of accreting white dwarfs (WDs) in Cataclysmic Variables. We use a synthetic photosphere and optically thick accretion disk spectra to model the COS spectrum as well as archival IUE spectra obtained decades ago, when the system was in an even deeper quiescent state. Assuming a reddening of E(B-V) = 0.06, an inclination of 60° (CW Mon has eclipses of the accretion disk), and a WD mass of 0.8 {M}_⊙ , our results indicate the presence of a 22-27,000 K WD and a low mass accretion rate \dot{M}≲ {10}^-10 {M}_⊙ {{yr}}^-1, for a derived distance of ∼200 to ∼300 pc.

Based on observations made with the NASA-Hubble Space Telescope.