Validity of the standard alpha-disk model

Establish whether the standard alpha-disk model adequately explains the observed ultraviolet and optical continua of accreting white-dwarf systems, including the systematically shallower observed spectral slopes.

Background

The standard alpha-disk model predicts continuum spectra that are generally bluer than those observed in many accreting white-dwarf systems. The paper explores empirical modifications involving a heated outer disk, but does not resolve whether the standard model itself is valid or which physical mechanisms account for the discrepancy. The authors characterize this issue as an ongoing matter of debate.

References

For four decades already, the validity of the standard $\alpha$-disk model has been questioned, mainly because disk models, as those generated using tlusty, have systematically disagreed with the observations: the continuum of the observed spectra have a shallower slope, or alternatively, the theoretical spectra are bluer \citep{wad84,wad88}. And while many explanations and solutions have been advanced, this issue remains a matter of debate \citep[see][and references therein]{zsi24}.

— The instantaneous mass accretion rate of novae in quiescence: - an archival ultraviolet optical spectral analysis  (2608.18037 - Godon et al., 18 Aug 2026) in Section 5, Discussion and Conclusions