Quantify optical-depth suppression of helium emission

Quantify, using numerical nebular-phase radiative-transfer models, the magnitude by which mixing of stripped helium-rich material into the ejecta suppresses optical helium emission at late times.

Background

The paper notes that ejecta optical-depth effects can suppress hydrogen features when stripped material is mixed into the ejecta, and it applies existing calculations to revise the hydrogen-mass constraint. A similar suppression is expected for optical helium features, but the authors indicate that the effect has not been numerically quantified.

Quantifying this effect is necessary for converting nondetections of late-time optical helium lines into robust limits on the amount of helium stripped from a possible non-degenerate companion.

References

A similar effect also influences the He\,\ features in optical, although, to our knowledge, no numerical models have yet quantified its magnitude in the case of He-rich ejecta.

— Constraints on the Progenitor of SN 2023bee from its Nebular-Phase Spectra  (2610.25674 - Coelln et al., 19 Oct 2026) in Section 3, “Narrow H/He Features and non-degenerate companion”