Far Ultraviolet Spectroscopic Explorer Survey of High-Declination Dwarf Novae

摘要

We present a spectral analysis of the Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of eight high-declination dwarf novae (DNs) 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 and 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 five objects (HP Nor, DT Aps, AM Cas, FO Per, and ES Dra), we obtain WD temperatures between 34,000 K and 40,000 K 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 T(eff) for catalcysmic variables above the period gap (approximately 30,000 K), similar to U Gem, SS Aur, and RX And.