Time-dependence of the UV resonance lines in the cataclysmic variables YZ CNC, IR GEM and V3885-SGR

Abstract

Orbital variations are observed in the UV resonance lines of YZ Cnc, IR Gem and V3885 Sgr. Optical spectroscopic observations of YZ Cnc show that the maximum absorption in the UV lines occurs about 0.7-0.8 orbits after the transition from red to blue of the optical emission lines. IR Gem shows orbital variations in the UV lines that are as strong as those of YZ Cnc. The variations in V3885 Sgr are more moderate, and may be orbital. Lines of the Si(3+), C(3+) and N(4+) ions vary in phase, which indicates that their regions of origin in the wind cannot be located far apart. Adding the present observations to earlier observations orbital variations in the UV resonance lines are concluded to be common. This suggests asymmetry in the inner disk region as the cause for these variations.