Far Ultraviolet Spectroscopic Explorer Spectroscopy of the Transitional Magnetic Cataclysmic Variable V405 Aurigae

Abstract

We present Far Ultraviolet Spectroscopic Explorer (FUSE) observations of the magnetic cataclysmic variable V405 Aurigae. Together with four other DQ Her-type binaries, V405 Aur forms a small subclass of intermediate polars that are likely to evolve into low magnetic field strength polars, similar to AM Her. Our co-added FUSE spectrum exhibits broad O VI and C III emission lines, in addition to a narrow O VI emission-line component that likely forms near the white dwarf surface. The O VI λ1032/λ1038 narrow emission-line flux ratio is near 2.0 throughout the orbit, which is indicative of its formation in an optically thin gas. Radial velocity measurements of the narrow O VI emission lines restrict any orbital modulation to a very low amplitude (K_WD=2.5+/-0.5 km s^-1), indicating, along with other single-peaked broad disk emission lines in the UV and optical, that the binary system is at low inclination.

Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.