Determine the origin of weak spectral lines in disentangled binary components

Determine whether weak spectral lines in a disentangled binary component arise from intrinsically weak stellar lines or from dilution by the flux of the companion, thereby establishing the correct flux-ratio scaling for the component spectrum.

Background

The spectral disentangling procedure produces component spectra whose absolute scaling is not uniquely determined. The authors therefore introduce a flux-ratio parameter, ℓ2=F2/(F1+F2)\ell_2 = F_2/(F_1+F_2), to rescale the component spectra before fitting them with spectral-synthesis models.

The unresolved ambiguity is whether a component’s weak absorption features reflect its intrinsic stellar atmosphere or are caused by dilution from the companion. Resolving this distinction is necessary for reliable determination of the component flux ratio and spectroscopic parameters, particularly in systems with unequal luminosities.

References

The component spectra derived from spectral disentangling can be arbitrarily scaled to match any flux ratio $\ell_2 = F_2 / (F_1 + F_2)$, since we do not know a priori if a star has intrinsically weak lines or if it is being diluted by the flux of its companion.

— Precise and Accurate Mass and Radius Measurements of Thirty Galactic Metal-Poor Stars in Detached Eclipsing Binaries  (2609.19248 - Rowan et al., 16 Sep 2026) in Section 4, “Spectral Disentangling”