CH in stellar atmospheres: an extensive linelist

TL;DR

This paper develops an extensive CH molecular linelist for stellar atmospheres, incorporating predissociation effects, to improve spectral analysis of stars, especially CEMP stars, and highlights the importance of molecular data in astrophysics.

Contribution

It introduces a comprehensive CH linelist with new levels and broadening effects, enhancing the accuracy of stellar spectral modeling and analysis.

Findings

Identification of strong predissociation CH lines in CEMP stars

Demonstration of CH features affecting spectra of barium stars

Highlighting the role of stellar spectra in refining molecular data

Abstract

The advent of high-resolution spectrographs and detailed stellar atmosphere modelling has strengthened the need for accurate molecular data. Carbon-enhanced metal-poor (CEMP) stars spectra are interesting objects with which to study transitions from the CH molecule. We combine programs for spectral analysis of molecules and stellar-radiative transfer codes to build an extensive CH linelist, including predissociation broadening as well as newly identified levels. We show examples of strong predissociation CH lines in CEMP stars, and we stress the important role played by the CH features in the Bond-Neff feature depressing the spectra of barium stars by as much as 0.2 magnitudes in the $\lambda=$3000 -- 5500 \AA\ range. Because of the extreme thermodynamic conditions prevailing in stellar atmospheres (compared to the laboratory), molecular transitions with high energy levels can be observed. Stellar spectra can thus be used to constrain and improve molecular data.