Separate luminosity-state effects from orbital modulation

Determine the relative contributions of luminosity-state changes and orbital-phase modulation to the observed exposure-to-exposure variations in YZ Cancri’s optical line strengths and profiles.

Background

The study compares isolated spectra obtained during quiescent and outburst-related states, but the observations lack reliable orbital-phase coverage. Because line strengths and profiles in dwarf novae can vary with orbital phase, the observed differences may reflect both luminosity state and orbital modulation. The available data establish an empirical state-associated contrast but do not resolve how much of the variation is attributable to either effect.

Phase-resolved, higher-resolution spectroscopy accompanied by simultaneous photometry would be needed to disentangle orbital variability from changes associated with the dwarf-nova outburst cycle.

References

The absence of reliable orbital phases prevents us from separating luminosity-state changes from orbital modulation. Because line strengths and profiles in dwarf novae can vary with orbital phase, orbital modulation is a plausible contributor to some of the observed exposure-to-exposure variations. The present data therefore establish a state-associated empirical contrast, while the relative contributions of luminosity state and orbital phase remain unresolved.

— A homogeneous analysis of archival and new low-resolution spectra of YZ Cancri  (2609.18646 - Dai et al., 16 Sep 2026) in Section 5.1, “State-dependent optical spectrum of YZ Cnc”

Such features require a harder ionizing field than the dominant Balmer and \ion{He}{I} emission, but the available spectra cannot distinguish among a boundary layer, inner-disk irradiation, stream impact, or short-timescale variability.

— A homogeneous analysis of archival and new low-resolution spectra of YZ Cancri  (2609.18646 - Dai et al., 16 Sep 2026) in Sections 5.2 and 5.3, “Specific line properties in quiescence” and “Limitations and future observations”