Resolve the spatial origin of composite line-profile components

Determine whether the broad-background and narrow-core components of YZ Cancri’s outburst-related composite line profiles originate in spatially separate regions or instead arise from a continuous, vertically or radially structured disk atmosphere.

Background

The outburst-related spectra contain composite profiles that were decomposed phenomenologically into broad-background and narrow-core components. At the available spectral resolution, this decomposition is nonunique and does not establish that the components correspond to physically distinct emitting regions.

The simultaneous presence of lines with different ionization requirements is consistent with a nonuniform accretion environment, but the current data cannot distinguish discrete layers from a continuous disk atmosphere with gradients. Higher-resolution spectroscopy is needed to resolve the relevant line profiles and constrain the geometry.

References

The decomposition of the outburst-related composite profiles is also nonunique at the available resolution. The broad-background and narrow-core measurements are useful phenomenological descriptions, but they do not prove that the two components originate in spatially separate regions. Similarly, the simultaneous presence of lines with different ionization requirements is consistent with a nonuniform accretion environment, but does not distinguish discrete layers from a continuous disk atmosphere with gradients.

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