Comparison of spectroscopic and photometric stellar parameter determination in carbon-enhanced metal-poor stars

• Published in: Astronomy & Astrophysics
• Main Authors: Heil Svenja, Juul Hansen Camilla
• Format: Article
• Language: English
• Published: EDP Sciences 2026-04-01
• Subjects: techniques: photometric; techniques: spectroscopic; stars: atmospheres; stars: carbon; stars: fundamental parameters
• Online Access: https://www.aanda.org/articles/aa/full_html/2026/04/aa57472-25/aa57472-25.html
• ISSN: 0004-6361; 1432-0746

Aims. The aim of this study is to evaluate the reliability of spectroscopic and photometric approaches for deriving stellar parameters in metal-poor stars, focusing on a carbon-enhanced metal-poor (CEMP) star with a well-studied very metal-poor star as reference. Methods. The determination of stellar parameters is first based on spectroscopy, where parameters are derived from Fe line equivalent widths using the 1D local thermodynamical equilibrium (LTE) synthesis code pyMOOGi. The second approach is based on photometry, employing colour–Teff relations, Gaia parallaxes, and bolometric corrections. Results. Analyses of the two stars reveal systematic discrepancies: photometric Teff, log(g), and [Fe/H] are higher than spectroscopic values. Offsets exceed uncertainties, mainly due to the limited Fe II line set and non-LTE effects in spectroscopy. Photometric based parameters prove more consistent and reliable, particularly when using (V–K) or (BP–K) colours. Conclusions. These findings confirm previous results and demonstrate that photometric methods yield more reliable stellar parameters, especially for CEMP stars than 1D LTE spectroscopic methods.