Obtain a robust near-infrared nickel diagnostic

Obtain a robust measurement of the Ni II 1.939 μm feature in SN 2023bee to provide an independent near-infrared constraint on the stable nickel abundance and the Ni-to-Fe ratio.

Background

The optical 7,200–7,300 Å complex used to infer the Ni-to-Fe ratio is strongly blended and sensitive to continuum placement, line identification, and signal-to-noise. The authors identify the Ni II 1.939 μm transition as a complementary diagnostic that could independently constrain the nickel abundance.

In the available FIRE spectrum, however, low signal-to-noise and strong telluric absorption prevent a reliable measurement of this feature. Higher-quality near-infrared spectroscopy would therefore be needed to resolve this outstanding diagnostic limitation.

References

In our case, however, the relatively low S/N and the strong telluric absorption blueward of Ni\,\ $\lambda19390$ preclude a robust measurement of this feature.

— Constraints on the Progenitor of SN 2023bee from its Nebular-Phase Spectra  (2610.25674 - Coelln et al., 19 Oct 2026) in Section 4, “Iron-group Line Diagnostics”