A Far Ultraviolet Spectroscopic Explorer Survey of High Declination Dwarf Novae

TL;DR

This study analyzes FUSE ultraviolet spectra of eight high-declination dwarf novae, revealing their white dwarf temperatures and accretion rates, and providing new insights into their accretion states and thermal properties.

Contribution

First UV spectral analysis of these dwarf novae using synthetic spectra, estimating white dwarf temperatures and accretion rates, and comparing them to known systems.

Findings

White dwarf temperatures between 34,000K and 40,000K for five systems.

Some systems are near the average white dwarf temperature for cataclysmic variables.

Spectral data suggest accretion states consistent with intermediate to outburst phases.

Abstract

We present an analysis of the FUSE spectra of eight high-declination dwarf novae obtained from a Cycle 7 FUSE survey. These DN systems have not been previously studied in the UV and little is known about their white dwarfs (WDs) or accretion disks. We carry out the spectral analysis of the FUSE data using synthetic spectra generated with the codes TLUSTY and SYNSPEC. For two faint objects (AQ Men, V433 Ara) we can only assess a lower limit for the WD temperature or mass accretion rate. NSV 10934 was caught in a quiescent state and its spectrum is consistent with a low mass accretion rate disk. For 5 objects (HP Nor, DT Aps, AM Cas, FO Per and ES Dra) we obtain WD temperatures between 34,000K and 40,000K and/or mass accretion rates consistent with intermediate to outburst states. These temperatures reflect the heating of the WD due to on-going accretion and are similar to the temperatures of other DNs observed on the rise to, and in decline from outburst. The WD Temperatures we obtain should therefore be considered as upper limits, and it is likely that during quiescence AM Cas, FO Per and ES Dra are near the average WD Teff for catalcysmic variables above the period gap (30,000K), similar to U Gem, SS Aur and RX And.