Insights from multi-wavelength observations during high and low states of non-magnetic CVs

Abstract

Close binaries containing a white dwarf accreting from a disk that receives material from a late stellar companion show an interesting variety of behaviors that depend on their accretion rates and the changes in this rate. The highest accretion rates are evident during the bright states of novalikes, as well as the superoutbursts of the shortest period dwarf novae followed by normal outbursts and the Z Cam systems. While the normal outbursts and superoutbursts of dwarf novae can be understood from the standpoint of disk and tidal instabilities, the changes in rates in novalikes when they enter low brightness states and the cause of extremely high rates for the systems with orbital periods between 3 and 4 h remain elusive. This paper highlights some recent insights and continuing problems found from X-ray, UV and optical observations of these high and low states, as well as the prospects for increased understanding from the anticipated future ground and space missions.