The boundary layers of weakly-magnetized white dwarfs ( WDs ) accreting at rates \hbox to 0.0 pt { \lower 2.5 pt \hbox { $ \sim$ } } \raise 1.5 pt \hbox { $ < $ } 10 ^ { 16 } g s ^ { -1 } are radially extended , hot , optically-thin , and they advect some of their internally-dissipated energy ( Narayan & Popham 1993 ) .
Motivated by this , I construct here idealized spectral models of an Advection-Dominated Accretion Flow ( ADAF ) around a WD , for application to quiescent Dwarf Novae ( DN ) .
The Bremsstrahlung cooling of the gas in the ADAF , with temperatures ranging from a few keV to a few tens of keV , can account for the X-ray emission properties of quiescent DN .
If the energy advected by the flow is thermalized in the WD atmosphere , the resulting emission from the entire stellar surface ( blackbody of temperature T _ { eff } \sim 5 eV ) outshines the X-ray luminosity substantially .
This extreme-UV component provides a flux in the 0.055-0.28 keV band which is sufficient to power the strong HeII \lambda 4686 emission lines of quiescent DN by photoionization of the disk material .
Reprocessing of the ADAF X-ray emission by a cold outer thin disk could also lead to an observable iron K _ { \alpha } fluorescence emission line , which can be used to probe the geometry of the accretion flow .
Existing observational data indicate that the presence of ADAFs in quiescent DN is not ubiquitous , while future observations , in particular with the X-ray satellites Chandra and XMM-Newton , have the potential to detect signatures of the hot flow in promising candidates .