Revisiting a Classic Stellar Tool: How Calcium Light Reveals the Metal Content of Stars

This paper revisits the Calcium II Triplet method for measuring stellar metallicity, using updated data and modern Python-based analysis tools. By recalibrating CaT line strengths across a large sample of red giant stars and adding the Gaia G-band, the authors produce a more robust metallicity calibration. The new results improve accuracy, especially for metal-rich stars, and better suit large surveys in the Gaia era.