Visibility of [Ne V] in the X-ray-detected little red dot

Determine whether the [Ne V] $\lambda3427$ emission line should be detectable in X-ray-bright, unobscured little-red-dot or X-ray-dot sources.

Background

The X-ray-detected VIPERS source is modeled with several accretion-disk and X-ray prescriptions. Its preferred model is broadly consistent with a radiatively efficient accretion disk and a relatively ordinary broad-line region, but the source lacks a demonstrated [Ne V] detection.

The [Ne V] line is used in the sample selection as a diagnostic associated with highly ionized gas and conventional type-I AGN. The authors therefore identify whether this line should be expected in bright unobscured X-ray AGNs as an unresolved observational issue.

References

Whether we should expect visible [\ion{Ne}{V}] $\lambda$3427 \AA \ is unclear, as even bright unobscured X-ray AGNs do not always show this line \citep{Reiss2025}.

— Extending the Little Red Dot population at intermediate redshift with VIPERS  (2609.10319 - Lisiecki et al., 9 Sep 2026) in Section “X-ray-FIR SED of V-XRD,” subsection “CIGALE modelling of the XRD”