A Far Ultraviolet Archival Study of Cataclysmic Variables: I. FUSE and HST/STIS Spectra of the Exposed White Dwarf in Dwarf Nova Systems

TL;DR

This study analyzes FUSE and HST/STIS spectra of five dwarf novae during quiescence to determine white dwarf characteristics, confirming previous findings and providing new insights into their FUV flux and spectral features.

Contribution

It introduces a comprehensive synthetic spectral analysis method for FUV spectra of dwarf novae, including treatment of hydrogen satellite lines and ISM modeling, enhancing system parameter accuracy.

Findings

FUV flux primarily originates from the white dwarf

Spectra exhibit broad emission lines

Combined FUSE and STIS data improve spectral fits

Abstract

We present a synthetic spectral analysis of Far Ultraviolet Spectroscopic Explorer (FUSE) and Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra of 5 dwarf novae above and below the period gap during quiescence. We use our synthetic spectral code, including options for the treatment of the hydrogen quasi-molecular satellite lines (for low temperature stellar atmospheres), NLTE approximation (for high temperature stellar atmospheres), and for one system (RU Peg) we model the interstellar medium (ISM) molecular and atomic hydrogen lines. In all the systems presented here the FUV flux continuum is due to the WD. These spectra also exhibit some broad emission lines. In this work we confirm some of the previous FUV analysis results but we also present new results. For 4 systems we combine the FUSE and STIS spectra to cover a larger wavelength range and to improve the spectral fit. This work is part of our broader HST archival research program, in which we aim to provide accurate system parameters for cataclysmic variables above and below the period gap by combining FUSE and HST FUV spectra.