The Geometry and Ionization Structure of the Wind in the Eclipsing Nova-like Variables RW Tri and UX UMa

TL;DR

This study models the wind geometry and ionization structure in eclipsing nova-like variables RW Tri and UX UMa using Monte Carlo radiative transfer, successfully reproducing key UV resonance lines and estimating mass loss rates.

Contribution

It introduces axisymmetric biconical outflow models for the winds in these systems, providing new insights into their geometry and ionization structure.

Findings

Models reproduce observed UV resonance lines in and out of eclipse.

Inferred mass loss rates are 6-8% of accretion rates.

Similar ion distributions and scattering regions in both systems.

Abstract

The UV spectra of nova-like variables are dominated by emission from the accretion disk, modified by scattering in a wind emanating from the disk. Here we model the spectra of RW Tri and UX UMa, the only two eclipsing nova-likes which have been observed with the Hubble Space Telescope in the far-ultraviolet, in an attempt to constrain the geometry and the ionization structure of their winds. Using our Monte Carlo radiative transfer code we computed spectra for simply-parameterized axisymmetric biconical outflow models and were able to find plausible models for both systems. These reproduce the primary UV resonance lines - N V, Si IV, and C IV - in the observed spectra in and out of eclipse. The distribution of these ions in the wind models is similar in both cases as is the extent of the primary scattering regions in which these lines are formed. The inferred mass loss rates are 6% to 8% of the mass accretion rates for the systems. We discuss the implication of our point models for our understanding of accretion disk winds in cataclysmic variables.