Origin of anomalous UV emission in unevolved FGK stars

Determine the physical origin of anomalous ultraviolet emission in apparently unevolved FGK stars and establish whether it arises through a single mechanism or through multiple evolutionary pathways.

Background

The paper analyzes 37 apparently single FGK-type main-sequence turn-off stars with anomalous ultraviolet emission, classified into three groups according to their UV excess. It combines stellar ages, chemical abundances, Galactic orbits, and inferred birth radii to investigate whether the groups share a common origin.

The results identify heterogeneous chemo-dynamical properties: the strongest UV-excess group has alpha enhancement and a Ti--Cr--Mn--Co abundance morphology suggestive of hypernova enrichment, while intermediate-UV stars show evidence of formation at smaller birth radii. The authors explicitly conclude that these findings do not establish a single causal pathway for the UV excess.

References

The origin of anomalous ultraviolet (UV) emission in apparently unevolved FGK stars remains unclear.

— The T-GEX project. II. Chrono-chemo-dynamic signatures of UV-bright FGK stars  (2609.19257 - Beltrán et al., 16 Sep 2026) in Abstract; Section 1, Introduction; Section 3.3.4, Chemical composition and the origin of the UV excess; Section 4, Summary and conclusions

Whether mixture-dependent metal-line blanketing connects this enrichment to the UV emission requires tailored spectral modelling.

— The T-GEX project. II. Chrono-chemo-dynamic signatures of UV-bright FGK stars  (2609.19257 - Beltrán et al., 16 Sep 2026) in Abstract; Section 3.3.4, Chemical composition and the origin of the UV excess