Phosphorus and near-IR diagnostics across cool stars, from solar analogs to P-rich stars and Cepheids

Phosphorus is difficult to study in the optical because useful P lines are scarce or absent in many cool stars. WINERED spectra in the Y and J bands provide access to multiple P I lines, allowing internally checked abundance measurements across different stellar types. The Y band also contains an important spectroscopic line He I 10830 Å, which can trace various astrophysical components like stellar chromosphere and exoplanet’s atmosphere.