Observations of Outflows in Cataclysmic Variables

TL;DR

This paper reviews observations and models of outflows in cataclysmic variables, highlighting their structure, driving mechanisms, and recent advances from multi-wavelength data, emphasizing the complexity and turbulence of these winds.

Contribution

It synthesizes current observational evidence and models of CV outflows, proposing a bipolar, radiatively driven wind structure with complex turbulence and vertical/azimuthal features.

Findings

CV outflows are bipolar, rotating winds driven by radiation.

Winds exhibit complex turbulence and structure.

Multi-wavelength data has advanced understanding of wind properties.

Abstract

Outflows in the form of fast winds from the accretion disk appear in nearly all high accretion rate cataclysmic variables (CVs), both novalikes (NLs) and dwarf novae in outburst (DN). The primary signatures of CV winds are broad, blueshifted absorption features and P Cygni profiles that appear in the ionized metal lines of lower inclination systems and the broad emission lines that appear in eclipsing systems. Much progress has been made in our understanding of the structure and behavior of CV outflows based on data obtained with X-ray, EUV, and UV telescopes and the kinematical models developed to fit the observations. Our current picture of CV outflows is that they are bipolar, rotating winds driven off the accretion disk primarily by radiative line driving from disk, boundary layer, and white dwarf radiation. Other mechanical forces may play a role in the formation of CV winds. The winds are highly turbulent and show complex vertical and azimuthal structure. Future work will focus on determining the physical, thermal and ionization structure of the winds and probing the mechanisms that govern wind formation and behavior.