Modeling the spectral signatures of accretion disk winds: A new Monte Carlo approach

Bipolar outflows are present in many disk-accreting astrophysical systems. In disk-accreting cataclysmic variables (CVs), these outflows are responsible for most of the strong features in the ultraviolet spectra of these systems. However, there have been few attempts to model these features quantitatively. Here we describe a new, hybrid Monte Carlo/Sobolev code, which allows us to synthesize the complete spectrum of a disk-dominated, mass-losing CV. The line profiles that we calculate for C IV resemble those calculated by previous workers when an identical geometry is assumed. However, our synthetic spectra exhibit not only the well-known resonance lines of O VI, N V,Si IV, and C IV but, with an appropriate choice of mass-loss rate and wind geometry, also many lines originating from excited lower states. Many of these lines have already been seen in the far-ultraviolet spectra of CVs obtained with the Hopkins Ultraviolet Telescope, the Far Ultraviolet Spectroscopic Explorer, and the Hubble Space Telescope. In order to illustrate the degree to which we are currently able to reproduce observed spectra, we finally present a preliminary fit to the Hopkins Ultraviolet Telescope spectrum of the dwarf nova Z Cam in outburst.