Inclination and orbital-phase-dependent resonance line-profile calculations applied to cataclysmic variable winds

The observed properties of wind-formed resonance lines in the spectra of nova-like variables and dwarf novae in outburst, are discussed. A method is then presented of calculating inclination- and orbital-phase-dependent resonance line profiles formed in a constant-ionization wind flowing from an accretion disc centre. The particular case of the CIVλ1549 line is considered. The line-transfer method used is based upon Castor's spherically symmetric application of the Sobolev approximation. The role of a wide variety of wind and disc parameters in determining the line-profile form, at both low and high inclination angles, is investigated. It is shown that the appearance of the resonance line profiles in low inclination system implies very gradual wind acceleration $$(\text{reaching}\, \upsilon_\infty \,\text{at} \,r$$ ⪢ 10¹⁰ cm) and that the lack of detectable absorption in the profiles of the same lines observed at high inclinations implies that the distribution of scattering ions is distinctly bipolar. In order to explain the frequent presence of redshifted emission in the CIVλ1549 line and its persistent absence in the Si IVλ1400 and N Vλ1240 profiles, it is argued that the C³⁺ ion density typically exceeds the densities of Si³⁺ and N⁴⁺ by an order of magnitude or more. This, in turn, points to $$\dot{M} \gtrsim{10}^{-10} M_{\odot}\,\text{yr}^{-1}$$. The behaviour of the C IVλ1549 line in high-inclination systems during primary eclipse is considered. It is shown that the presence of the accretion disc alone is sufficient to induce a bipolar line-emissivity distribution in the plane of the sky. However, deep line eclipses may be averted by the existence of a column of absorbing wind material located over the bright disc centre. The line eclipse light curve is found to be extremely sensitive to both the inclination angle and the ratio of the secondary star radius to the orbital radius, but rather less sensitive to the wind mass-loss rate, outflow geometry and velocity law. To resolve the predicted structure in the line eclipse light curve, a phase resolution of $$\Delta \phi \sim0.005$$ is needed. Application of the eclipse calculations to IUE observations of RWTri and UX UMa again suggests a wind mass-loss rate $$\gtrsim{10}^{-10} M_{\odot}\,\text{yr}^{-1}$$.